Has this ever happened before? I'd assume that you'd have to accidentally come into contact with some shady mafia group over e.g. Bisq for that to even be a remote possibility.
It hasn't happened to me myself, but it has to other people. Someone here in the forum also reported about it in the german local board. Can't find the thread right now. But I can remember that he sold bitcoins for 500 and received counterfeit money. He only noticed this when he wanted to deposit the money at the bank. Unfortunately, he did not report further whether the buyer could be caught with the counterfeit money. 