Well that guy that sold it probably got the dumazz of the day award for that area.Every flea market in the South has a least one booth where some guy is selling guns, and has been doing so for years.
The only locally that has ever gotten busted was one where the undercover agent told the seller that he had a buddy who had just got out of prison and needed a gun, seller told them to meet him at his house, and he proceeded with sale to an actual felon while the ATF agent watched.
Even so, the seller was only charged with selling to a felon, not being an illegal dealer. The proof to show that someone meets the legal definition is too involved, and too time consuming for ATF when there is so much other low hanging fruit.