Had a slide incident once at SMF a few years ago while I was waiting for a flight. Slide deployed because 1R was still armed and when the door was opened for the catering truck - BAM! Fortunately nobody was hurt but the aircraft had to be taken out of service. I asked a F/A about it when I boarded my flight (on a different carrier) and she told me that it was something like $10,000 to replace an accidentally deployed slide. And the in-flight crew on that aircraft had some 'splaining to do to their bosses...

In your example it sounds like the pack itself fell off the door but didn't deploy?