Have you contacted the buyer directly?
I once bought some pinball items and the next day I found a fraudulent charge from a day or two earlier. Fast forward 2 weeks and I find out that the card company cancelled all transactions after the fraudulent charge including my legit purchase. I only found out because I paid with PayPal and they froze my account until I straightend it out.
So while it may be a scam it sounds like it could also b an honest mistake