Good question.
Also, some enterprising journalist would be able to trace the call.
The cell phone company would have a record of the cell tower from whence the call was transmitted.
That phone call was so phony (no pun intended) that someone should track down where it came from. I can't believe that anyone (he AND his staff would have had to have overlooked his cell phone) would that irresponsible (especially since this is the second time it has happened)--to accidentally be THAT rude and THAT inconsiderate.
Maybe he thought it was humorous,,,but even if that was his intent,,,,it shows horrible judgment given the nature of what was publicized as an important speech.
In any event, it shows how little class Rudy has.