I don't think you'll dare to withdraw such funds that you don't even know where it comes from, or let's say you have won from one of your gambling games, but still you know the amount you have won, so it's actually unreasonable if you withdraw such funds that you don't even know where it comes from. If you are a reliable and reputable person, you won't touch the money, but if you want to take advantage of the chance, surely you will quickly withdraw the amount and just pretend that you thought you are only withdrawing your own winning funds.
That's only happen in Japan.
The reality most people don't care where the money they got, either wrongly transferred by casinos, banks, friends etc including the money/wallet that dropped on the street, they will grab it ASAP.
Regardless they pretend they don't know about the money, in the end they need to give back.