Say you do run the numbers and it comes back stolen. You start a chain of events that (assuming you traded with an established member, not a new guy with evil intent) may go back several trades and owners. You give up the stolen gun, whomever you traded with has to return the one you traded and he contacts the person he got it (the stolen firearm) from, everyone has a conversation with LE explaining the chain of ownership until it gets to someone who can't explain/prove where they got the firearm? Is that how it would theoretically work?