Well, let me just say that L is a major dickhead, and I'd kick his ass big time. That being said, yes, the gun is yours. But, the guy who bought it isn't obligated to give it back to you. If you want a guarantee that you'll get the gun back, you report that the gun was stolen by L. and then sold to the uncle. The police will go in and confiscate the gun as stolen goods, and you'll have your gun back. Of course, it will probably go to trial, and all of this will come out there, and it will be for a judge/jury to decide, but I'd be willing to bet that you'd win.
Now, as for the uncle, I don't know...I mean, he's already asking questions like "is the gun hot, blah blah?" What kind of upstanding guy is he? I'd get L. to get the money he got from his uncle, take the money to him and get your gun, which he then returns to you. You shouldn't be buying your gun back. In the eyes of the law, L. stole it, and sold it, which in criminal speak is larceny and sale of stolen goods.
Good luck, and I'll make sure never to loan out my Kate Spade bag
