DLPhoenix

Last night I was scheduled to fly PHX->LAS->ICN with the first leg on US air.
Upon boarding we were notified that the flight is held since there is an "absolute need to wait for a pilot that has to fly an airplane from LAS to the east coast tonight".
The flight ended up arriving in Vegas an 1:15 behind schedule. I barely made my connection, but a few others missed their connections.
US could have sent the pilot on a Southwest flight that departed Phoenix an hour later.
While we were waiting the supervisor that was brought to handle the situation kept saying that this is an "absolute must" and that we are not entitled to any compensation.

Can an airline hold a flight for such a reason?
Can I file a complaint with the DOT/FFA? If yes where?

Thanks,
DLP