Am I missing something? He tried to leave - twice. Who stopped him?

If no one stopped him and he consented to the search, then too bad.

If someone from the TSA actually detained him physically, I hope he goes after the evidence in court....he should have knocked the detaining screener on their butt and then made a run for it. That should be legal self-defense, since the TSA does not have authority to physically detain anyone.