Ok, so I post a pic of a gun with the serial number on it or you write down the serial number in a FTF and then later claim it was stolen. How are you going to prove ownership? You simply can't. I will prove you wrong and you will (hopefully) be charged with filing a false police report and/or forging a false bill of sale (fraud).
Good luck. (tick tock, tick tock, tick tock, tick tock)
Good luck. (tick tock, tick tock, tick tock, tick tock)