As a consumer I had no way of knowing the motorcycle I bought was stolen. It came with the keys, the title, there was no evidence of thievery (most commonly broken parts around the ignition). The police said, "Wow we wouldn't have known this was stolen without running it in our database either".

I didn't know. But it still gets repossessed, and I'm still out $1k.

(True story, and my first brush with the laws around black markets)