There are many ways to lock a car door,
Please don't insult my intelligence. Every car I've ever owned can be locked without a key. That's the one thing I was absolutely ridiculing in the story. Snap the lever, or depress the button (or whatever the mechanism is) to "lock" and then close the door. Done. Period. Car is locked up. No sophistication involved. No devices involved. A ten year old can do it (and often does to the chagrin of its parents.)