Buyer requested return, I declined. Hopefully nothing happens.

On 5/22 I sold a switch game for $30. It was delivered on 5/29 and I thought everything was good. Then yesterday (6/2) the buyer requested a return and put “ordered by mistake”, I declined the return as im a no returns seller. What I think happened is the buyer played the game and beat it and now they want their money back. Hopefully they dont try to do a chargeback with their bank. Anyone have something like this happen?