Make sure you stay far away from anyone trying to sell you stolen merchandise. It’s the not oft used scammer code of ethics. A good person wouldn’t be buying something stolen so it’s ethically ok for them to take your money. If it’s a legitimate shop (like it sounds like it may be) what you might do in the future is buy those $50 (or more) visa gift cards and start a paypal account with those. Or you could even pay for the item with it (assuming they take credit cards). Just make sure you don’t get one for much more then the item is worth in case they (the shopkeeper) try to pull a fast one on you. If the offer from the shop isn’t time sensitive, I would wait for them to send back the money order. You might be able to take your money order stub back to the issuing bank and get them to refund the money. Explain the situation to them. Hopefully, they’ll be reasonable.