Air carrier Flight Attendant reported that after the last flight; a door was left armed and resulted in the escape slide pack falling out of the housing when catering opened the door.

Narrative

During boarding of flight; a supervisor came on board to inform me that the 2L door on my last flight; ZZZ1-ZZZ; Flight ABCD; was left armed. The supervisor further explained that when catering opened the 2L door to cater the AFT galley the slide pack began to fall out of the slide pack housing. The caterer stopped opening the door and was able to prevent the slide from deploying and then contacted maintenance. This event did not result in an inadvertent slide deployment (ISD). On flight ABCD; ZZZ1-ZZZ; I was working the FA A position assigned to arm/disarm door 2R; cross check door 2L; and sit at jumpseat 2R outboard. When we blocked into the gate at ZZZ; the seatbelt sign was switched off; I unfastened my seatbelt; disarmed the 2R door; and looked at the 2L door and cross checked it. There was a brief delay from the Purser to conduct the all-call to which the AFT contacted the FWD and then the purser conducted the all-call per SOP. No other irregularities occurred at the time; in my experience. It was after the fact that I was made aware that the 2L door was not disarmed and cross checked properly.