I used to have an older car that didn't have a key remote, so I was in the habit of locking the door as soon as I opened it. I broke that habit on my last car, but I would lock myself out occasionally, but I had a spare in my wallet. And I smoke pot so memory isn't always 100% lol.
This last time however I was at a meet, had my new camera and was snapping pics. Car was locked, but I went to my car and opened the trunk only (doors stayed locked) and set my keys down to grab my other lens. Put on lens, shut trunk, then realized I didn't have keys. #potheadproblems lol