I takes nerve to contact and then try to "sell" the bike back to the person you stole it from. So I'm leaning towards the "person with bike" being legit and trying to get the bike back to the original owner. And if I were them, I'd want to sell it back to the owner for at least as much as I paid the thief for it. The law (about not being in possession of stolen goods and losing what you paid for those stolen items) is the reason nobody ever calls the cops when they think they bought stolen goods. The buyer of the stolen goods is the only one who gets screwed, when they are trying to do the right thing.