I left my friend in my car as I ran into the store and I locked him in. He got out of the car, setting off the alarm. He said he simply locked and shut the door to stop the alarm, because the alarm was not going off when I returned. I did not witness this, but there was no damage or evidence of other action.
Since then (as in I can honestly confirm that at no time before did these problems ever occur and have been present immediately henceforth from that alarm being set off) the horn does not work on my 2006 Honda Civic, and there is no beep notification that used to accompany my second time clicking the lock button on my remote. Absolutely nothing else in the car is not working or behaving abnormally.
Either something went haywire electrically at that moment exactly or some system simply needs to be reset, I need advice. thanks.

 

Did you check the fuse for the horn?