It is just an observation, but one that nobody else seems to have made. I am not aware of any unmodified vehicle which cannot be opened from the inside. Even if the rear doors had "child proof locks" which may prevent opening from the inside if it was a passenger sedan, I would be very surprised if the sliding door, and both of the front doors, did not have a lever to unlock the door. If a 7 year old became aware that they were trapped in the vehicle, wouldn't they have time to find that lever, usually very near to the door handle, before they suffocated, or am I expecting too much?