Come fly the f&$%ing skies

A flight from Las Vegas to Detroit was canceled after the captain was heard cursing into his cell phone in the bathroom, then came out and cursed at the passengers. My question is this: how did the passengers know he was cursing into a phone? We've all had moments in the bathroom alone that involve some foul language.

If I were a passenger on that cancelled flight, I would have some four letters words for the captain.