Yeah, well you shouldn't have sold that account. You basically said that you got the account from a friend and that you were "assuming it is pretty safe" and "im pretty confident". Anyway, wasn't it a friend who gave you the account, so unless you or your friend is a scammer this shouldn't have happened. You trusted your friend not to scam, so that makes you responsible. Either way, it doesn't matter. Clearly this was an account loan, which isn't really allowed on the forum anyway, but selling an account that you know is going to get recovered is your fault, I don't know who you want to pin this on. You should not have sold the account period. Of course, Silver shouldn't have bought the account, but he's the one who got scammed here.
You clearly don't want to refund. You made a mistake, when you want to refund the 20M, you can refund him and appeal. For now, you will be banned.