i have a puzzle. can there be two people in the same neighborhood who's car door opener part of the keys work on each other's car?
It certainly used to be possible with some of those devices for a 3rd party to pick up the signal that your door opener transmits and, if the security isn't particulary strong [which when they first appeared was the case], mimic your door opener in the future and (un)lock the door.
e,g for some, the code the opener sent changed at each press and the car knew the sequence. In case you stand in the pub pressing it, the car usually accepts the next n codes in the sequence and will open the door if it gets one of them. If the sequence is easy to predict someone else can predict it.
But that would imply someone [at one time] close enough to pick up the signal as well as your car getting it, and, at the time when your door is locking, they must be sending it fairly close too.
If it happens exactly as you reach the door it sounds suspicious...a fault would more likely lock the door more randomly than that. That said, if it is someone, they are clearly comedians rather than crooks, since they are advertising they can do it, I doubt they'll pinch your car.
You'd need to google for the specific device or van to get more specifics though.
I would have thought there must be some around now that are much more difficult to open though, so perhaps it's just a fault.