In the Sia-UI Terminal plugin can you run consensus status and then wallet and post the results? You should never "lose" money as long as you send it to an address you own, but if your client's blockchain isn't synced it might not be aware that it has more money. Additionally if not enough blocks have been mined since your transaction (usually 144 so ~a day of waiting) your wallet won't show your new funds.
TLDR: It'll take about a day to see your funds, and you can only see them if your client is synced.
It looks like its an amt sending error...I used the terminal to work it out and the amt you enter is not what is in your wallet and is expecting a unit which is all a bit confusing but got there in the end.
The smallest unit of siacoins is the hasting. One siacoin is 10^24 hastings. Other supported units are:
pS (pico, 10^-12 SC)
nS (nano, 10^-9 SC)
uS (micro, 10^-6 SC)
mS (milli, 10^-3 SC)
KS (kilo, 10^3 SC)
MS (mega, 10^6 SC)
GS (giga, 10^9 SC)
TS (tera, 10^12 SC)