Don't some modern cars auto-lock themselves anyway once the key's out of the ignition?
My son was in a similar situation years ago - due to his autism (people on the autistic spectrum have very strong habitual behaviour, things MUST be done a certain way every time), he had the opinion that once you got into a car, everyone HAD to lock their doors and put the seatbelts on. He pushed his door button down... but my mate's keys were in the boot!
Nowhere near the same urgency as this thread - after a couple of hours the AA got in.
Diff.