I had this happen like 3 times in 10 years and 2 of them were very memorable... Drive Up ATM, and Movie Theater Parking lot. Anyway my horn is in a pile of useless parts since one day I was removing the crash bumper and saw it... (oh thats where the horn is...) no more.

It was so completely random I had no idea where to start looking. Figured it was some parting DHP gift from Charles.