The Unintentional Thief

I think I’ve been the victim of a reverse scam. Is such a thing even possible? I guess it is when someone comes to your yard sale last Saturday, buys a few items with cash, says he'll be back to get them, and never returns. So I have his $18, plus some things that I could sell to someone else if I was the cruel type. Not to mention I also appear to have the key to his pickup truck, which probably explains why he hasn't come back. He was driving a small van and since he also bought some large pieces of furniture from my neighbor, he said he would go get his truck and come back. We know nothing about this guy and haven't heard a thing from him.

Is he some sort of yard sale fairy godfather who goes from house to house spreading money and good cheer, and leaving the goods so that we can make double money off of our stuff? Or is he going to show up in 6 months demanding his stuff that I will have eventually given in and gotten rid of the day before? Sadly, I'm going to have to guess it will be the latter.