Sorry mate, there's nothing anybody can do. If something or somebody sends your coins, then they're gone.
Remember that with Sia, as with any cryptocurrency, you are responsible to secure your computer and anything that runs your coins. It's just like being a bank or an exchange. It's no accident that banks and exchanges spend a lot of time and resources securing their servers, and that they establish strict processes to avoid "fat-finger" type mistakes where somebody mistakenly makes a transaction with incorrect parameters (wrong address or amount).
