I would never allow my child to be dropped off by the busload to an airport. Especially if there were ZERO chaperones in the airport. I have seen too many groups of minors misbehave and get into trouble at airport even with chaperones.
Latest point, in Orlando last month a few people from a group of 30 were doing wheelchair races with airport wheelchairs. One ran into another passenger. Airport police wanted to kick the entire group off of airport property, regardless of who was pushing who. The only thing that saved them was the group of chaperones finally took charge and promised to make every person remain seated until the flight.t.
I wouldn't want the liability of being any part of a summer camp that drops off a busload of kids--at an airport, bus station, train station, etc, and expects them to be on their own from here.
OP said "luckily" someone was able to come back. Well, if they weren't so lucky, or if the kids didn't have contact info for the camp 'in case of any travel emergency or missed flight', Atlanta police would have likely not allowed the kids to sleep at the airport.
In ANY case (not just IDB--equipment/weather cancellation, or a kid who stayed at McDonalds or was at the wrong gate), it would have been embarrassing, to say the least, when the parents found out that their kids were in the custody of child protective services due issues the camp could have avoided.