Originally Posted by
xliioper
I don't believe TSA actually confirms your check-in status now that they just scan your ID and the system only checks if you have a same-day ticket from airport. How he got on the aircraft without a BP would be the bigger question mark.
Another, albeit less likely, scenario is they were connecting from a separate ticket. But that just explains not passing through security (while also not being checked in). How they got on board is the more interesting question.