My old car had a bug or something where if you left the car running, even if you made sure to unlock the door when you got out, it would still automatically lock the door after a minute. Either you had to turn off the auto-locking feature (which I did), or leave the door open with the car running.
I was way out in the middle of nowhere driving between Burns OR and Ontario OR. I had to stop and use a rest stop restroom, and I forgot all about this and left he car running (it was not long after I got the car). I came back, and the car was running, but all the doors were locked. No cell phone service, no cars driving by, and nothing around to try slipping in the window to unlock the door. I eventually had to chuck a rock through the back passenger window.
The truck I have now has keyless entry and auto-locking doors, but not that problem where it would lock itself no matter what after a minute.