Reminds me of an episode of car talk. Caller says he parked his car and locked it before work. After work he goes to the parking lot to find his car missing. Before he can call the cops though, he sees that his car has been moved to a nearby spot. Nothing taken or broken, but the seat adjusted, radio station changed, and it’s locked. Caller wanted to know what the heck happened.

To the best of their abilities, the car talk guys surmise that someone with a similar car had the same key as the caller. They unlocked it and started the car without realizing it was the wrong one, drove a little before they realized their mistake, then parked and left it.

I forget the exact details, but I guess it was a cost saving measure to only make so many key variations.