Since the money was given to him in error, he can’t be held liable for the loss. If it’s gone, it’s gone.
Taking the money to a casino is one of the oldest tricks in the book for keeping money out of reach of creditors. The moment he gives the money to the casino, it’s gone, there is no trail, because in many places you don’t have to show an ID when you cash in tokens. Otherwise he’d need one or more accomplices who could claim that money as tax-free winnings. I’m pretty sure that also works somehow with online gambling sites.
