I did get caught up and leave a store with something.
I picked it up, but then decided not to buy it. But I didn't want to just put it down anywhere, I wanted to put it back where it belonged and was going to do so after I browsed.
When I was done browsing, I thought, "Nothing I want to buy," and proceeded to leave the store.
When I got outside and realized I was still holding the thing, I went back in and paid for it. I didn't even want it, but I felt guilty for having shoplifted the thing, lol, so I paid for it.
It really does happen that people absentmindedly leave a store with something.