During deplaning a passenger informed the reporter that a cabin door was never armed during the flight. Checking later the door was found to be presently armed and the reporter believes that she was moving the lever during departure and arrival duties without actually checking the position.

Narrative

Upon deplaning a male passenger casually said to me; 'that door was not armed the entire flight.' I replied that it was armed as I had armed the door myself and I had disarmed the door myself upon arrival. Once all passengers had deplaned; I verified once again that my door was disarmed. To my surprise and horror; I was alarmed to see that the door was actually armed. I realize that I had automatically raised the plastic cover and rotated the lever to the opposite position; both on departure and arrival. Another flight attendant and I then gave each other the thumbs up believing arming/disarming of our respective doors had indeed taken place. I did cross check her door in both instances and visually saw red and green respectively. I realized that my door must not have been disarmed when the flight arrived. My arming and disarming duties were performed out of habit rather than in the moment being fully aware of which way I was pushing the lever. The man who brought this situation to light had long since deplaned. He made the statement so casually; and now I wonder why he didn't bring the situation to a flight attendants attention during the flight. I am startled that this situation occurred; as I was confident in my responsibilities. I make this report because I am alarmed that I was actually disarming the door when I believed I was arming the door; and actually arming the door when I believed that I was disarming the door. I went through the automatic motions without being fully aware of what I was doing. Please make other flight attendants aware of becoming complacent on our routine activities.