He says it was an in-joke with his friends about the way he looked. From that I would like to abduce the fact that the friends the message was addressed to wer

He says it was an in-joke with his friends about the way he looked. From that I would like to abduce the fact that the friends the message was addressed to were not in the airport (at least not all of them) otherwise he wouldn't be informing them he's going to his flight. Based on that, I have a hunch the message was "intercepted" by one of his friends' parents who freaked out and told the cops who raised the alarm. That would be the easiest way to explain how the message was "picked up" in the first place.