For several years, I have heard most young people and some adults use the phrase What happened? when they do not hear what is spoken. It appears to be used where previously several other phrases were used, the most formal being I beg your pardon. (See How do you decide which phrase to use when asking people to repeat what they said?)
My answer to What happened? is usually Were you expecting something to happen? or Was something supposed to happen? I am met with a look of puzzlement or annoyance.
I wonder what the origin of this usage might be. Perhaps it is considered too humiliating to beg someone's pardon? Similar queries may be taken as an admission of fault (not paying attention). Can someone provide some insight?