A B737-NG Flight Attendant opened the L1 door with the slide armed after being distracted by other crew communications. The slide did not deploy because the Captain assisted putting the slide pack back in the casing.

Narrative

After 18 years of arming and disarming aircraft doors; I failed to do so upon arrival. I was looking through the port hole to ensure the agent was present and the jetway was close to the aircraft before I disarmed my L1 door. I was preoccupied with the F/D door opened; the Captain walked out and I was anxious to know if we were changing aircraft for our return flight. He gave me the information then 'knock; knock' the agent was at the door. I proceeded to open L1 only to have the slide pack fall out of its casing onto the floor. The door was open 1/4 of the way. The poor agent jumped way back; and I dropped to my knees to hang on to the slide pack; thinking that the girt bar had slipped out and got caught. Then I looked down to realize the girt bar was still in its brackets! I commanded for the First Class passengers to stand back; twice I had to tell them. Luckily; Captain was standing there and he was able to assist me in securing the slide pack back into its casing by disarming it and gently pushing it back in. Maintenance showed up and was able to open our door and said it was OK to deplane. It all happened so fast tht even the First Officer had no idea it happened; since deplaning was only held up a matter of minutes.