I have been ripped off at Ebay. But it was one time in about 60 interactions. Yes, the seller did close the Ebay account shortly after the transaction. I was angry. But on the whole, I have saved so much money that far due to Ebay that this loss is small fish.

I've decided after some days to do nothing at all (which is my advice) after having thought how much more anger, frustration and time I would have to give to that single instance of being ripped off. The probability of success was low (imagine the guy is really bankrupt; who's going to pay?), the amount of money lost was still low (though more than your loss) compared to the usual gains.

I felt good (after some days of anger) to let loose. Cut the losses and don't let revenge or the thoughts of getting even) ruin the next couple of months.

But that advice is restricted to minor losses. In Fionn's case, I also would have done everything I could to recover the instrument.

Wolfgang