It's nothing. Totally not mine. I totally didn't borrow your Jeep the other night to pick up chicks and forget I left that in there. Nothing to see here.
You might want to check your door alignment and look around to see if any screws were missed
(Full disclosure, we determined that my old TJ was most likely a Friday build (or Monday after the superbowl) - it had some ummm...minor discrepancies.)