@gigacoin
This is impossible. You can not unlock anything if the wallet.db is deleted. You can only create a new wallet or restore from seed.
If you can't restore with your old seed but can restore with the new seed, you have an error in your old seed.

So I am sure your wallet.db did not get deleted.
If you can unlock (without restoring) your wallet, you have not deleted the (right one) wallet.db... Or the Sia daemon was still running when you deleted and thus the file got recreated.

So, to be sure, try without the UI.
start your command line (cmd.exe).
Type

cd <full path to your unzipped Sia-UI>\resources\app\Sia\
start siad.exe
siac wallet init-seed --force

write your old seed when prompted.

What is the response after that?
Does siad open a new window and show something?

Besides,
did you see any coins in your wallet at some point of time ever? What and why do you expect to discover in your wallet? Did you transfer coins to your old seed address from exchange or mining pool?

I lost my sia wallet but I still have the seed for my old wallet. So I created a new wallet and then I recovered my old wallet and my siacoins using "wallet load seed" in terminal. But I have a doubt.

1st doubt: When I recover my old wallet what exactly is happening......
(i). Is my new wallet joined and synced with my old wallet in which case I can use any of the two wallets for transaction purpose
OR
(ii) Is my new wallet replaced with old wallet in which case if I do any transactions my old wallet is going to be used
OR
(iii). All of my old wallet Siacoins are transferred to my new wallet in which case my new wallet is going to be used for transactions?

2nd doubt: After I recover my old wallet, if I have to mine Siacoins in future which wallet address do i have to use...the old wallet address or the new wallet address?

@gigacoin
You are doing right, The UI creates an empty wallet.db.
It appears to be working normally, the blockchain syncs.
Just when you try to open the wallet, The UI will see there is no initialized wallet and will ask what to do.
It is easier to restore the wallet with the old seed than to load into a new wallet.
Perhaps it is easy enough to load the old seed into a new wallet, but I've seen repeatedly people asking what is going wrong doing that. So I have the impression it is easier to restore the wallet from seed than to load it into a new.

Technically loading an old wallet into a new one should make a new transfer transaction where all available balance is transferred into the new wallet. The old wallet is not erased from the blockchain. It gets simply emptied.
So in your particular case it could be that you succeeded in loading the old wallet and emptied your old.
So if you successfully restore your wallet and it shows 0 balance you should see a transaction transferring your coins.
Then you should restore your new wallet with your new seed.

I have just tested.

1. Made a wallet via
   siac wallet init -p
   and set a password.

2. Unlocked the wallet with the set password (different from seed).

3. Then shutdown siad process and delete the wallet.db file.

4. After starting siad no wallet found, can't be unlocked via password or seed.

5. recovered wallet via "siac wallet init-seed" and the seed (generated at creation time). No password was asked.

6. Try unlock with password (set at first creation) gives error "Could not unlock wallet: error when calling /wallet/unlock: provided encryption key is incorrect"

7. Try unlock with seed as password, gives no error:

 /sia/bin/siac wallet unlock
Wallet password:
Wallet: scanned to height 118844...
Done!

Bingo! Restored and unlocked. Password is reset to the seed. And can be changed to encrypt the local wallet again (since version 1.3.0.).

@bryan

siac wallet init-seed

is the command not

siac wallet load

if you want to recover your wallet.
with load you load some old wallet into a new one.
Though, I'm not sure how should a wallet work properly with more than one seed loaded simultaneously.

That WIKI could be something from old times...
My node shows me:

siac wallet -h
Generate a new address, send coins to another wallet, or view info about the wallet.
...
Usage:
  /sia/bin/siac wallet [flags]
  /sia/bin/siac wallet [command]

Available Commands:
  address         Get a new wallet address
  addresses       List all addresses
  balance         View wallet balance
  change-password Change the wallet password
  init            Initialize and encrypt a new wallet
  init-seed       Initialize and encrypt a new wallet using a pre-existing seed
  load            Load a wallet seed, v0.3.3.x wallet, or siag keyset
  lock            Lock the wallet
  seeds           View information about your seeds
  send            Send either siacoins or siafunds to an address
  sweep           Sweep siacoins and siafunds from a seed.
  transactions    View transactions
  unlock          Unlock the wallet

Flags:
...

Agreed, deleting the wallet and recreating from seed is a bit shooting with a bazooka instead of a sniper rifle. That makes only the SC balance survive. But you can't recover your files or contracts anyway yet.

In other words, is there a way to get my wallet balance having my public key?

@moorsc0de
There is connection between SiaHub where I watch the pricing trends and a UI (the underlying wallet or siad).
Siahub shows the data (pricing and scoring) it gets from a "Siahub wallet". You can get the same information from your wallet. The host score differs slightly between any 2 wallets but the price offerings are correct. The "laggy" comes from the fact the wallet does not update all the hostdb every second.
And I saw hosts with nearly zero "price" but insane fees in the top30 before the 1.3.0 wallet was available. I saw these hosts pushed out of top 300 after the 1.3 version was in the GitHub. So I assume the wallet version lower than 1.3 still does not penalize them.

Regarding contract fees- 3-5 SC are normal one time fees in my opinion.
Of course, 250SC just for initial renter setup (50 hosts) looks a lot , but that is the price you pay the hoster for being ready to accept your files (locking part of the hosts collateral). Upload and download fees are infrastructure related- someone has to pay for the used bandwidth. Why should the hoster alone bear all the responsibility and costs for the renters wishes by sacrificing his available coins, storage space and network bandwidth?

Sia ui 1.2.2
Linux64 system, wants to recover the coin from the wallet.
I have an old seed.
I created a new wallet and at the terminal I typed wallet load seed and current password and seed of old wallet and shows an error
Usage:
/media/WAŻNE/avast/SIQ/resources/app/Sia/siac [flags]
/media/WAŻNE/avast/SIQ/resources/app/Sia/siac [command]

Available Commands:
bash-completion Creates bash completion file.
consensus Print the current state of consensus
gateway Perform gateway actions
help Help about any command
host Perform host actions
hostdb Interact with the renter's host database.
man-generation Creates unix style manpages.
miner Perform miner actions
renter Perform renter actions
stop Stop the Sia daemon
update Update Sia
version Print version information
wallet Perform wallet actions

Flags:
-a, --addr string which host/port to communicate with (i.e. the host/port siad is listening on) (default "localhost:9980")
-h, --help help for /media/WAŻNE/avast/SIQ/resources/app/Sia/siac

Use "/media/WAŻNE/avast/SIQ/resources/app/Sia/siac [command] --help" for more information about a command.

When I use the recover seed option and give an old seed it writes a recovering seed, scanning the blockchain, and is eror

Sia-UI wallet error
Socket hang up

Siad has exited unexpectedly. Please submit a bug report including the error log here.

Error Log:
Loading...
(0/6) Loading siad...
(1/6) Loading gateway...
(2/6) Loading consensus...
(3/6) Loading transaction pool...
(4/6) Loading wallet...
(5/6) Loading host...
(6/6) Loading renter...
Finished loading in 1.010121972 seconds

Hello.
I made an address in SiaUI by typing wallet address, and ive been mining with that for a little while now. I was wondering why the balance in the wallet wasnt changing so i eventually figured out that i needed to unlock the wallet and press recieve transaction to find my own wallet address...

But is there a way to get access to the wallet address that i made and move the funds into my SiaUI wallet address

Edit: So i figured out that i have a whole bunch of addresses in the SiaUI which all work towards the same wallet.
But i still dont know how to get the SC to show up in the wallet.

As above, my wallet wouldn't open after I moved it from the desktop to a new folder with the rest of my crypto wallets.

I had a good look around on here and followed someone's advice to delete the local .json file in my users/appdata file. Clearly that hasn't helped...

I made a complete USB backup of the Sia UI folder before messing around with it but if I open it from the drive, it just looks like a brand new wallet that refuses to sync. Also, I can't find the option to recover wallet from seed? The only option I could see was to create a new wallet which I have now done thinking that it would allow me to revover my old wallet afterwards (it's still syncing).

I tried to remove the entire Sia folder within appdata hoping that it would see my PC as a fresh device and create a new folder structure but that hasn't worked.

Can anyone explain how best to get access to my old wallet and coins again, please? If i've shot myself in the feet, i'd rather know sooner than later as i'm still mining to my old wallet address.

Thanks in advance!