Ask google/audi/mercedes/bmw/toyota/etc for help. They've spent billions on trying to determine if an object is a ball, cat, dog, human, car, truck, etc. I might be wrong but there is probably no way to discriminate with any significant precision between a car and any other largish object getting near your truck on a normal person's budget.
I would suggest you use the normal shock/vibration detector that is already used in car alarms to turn on a camera and get photo proof of the incident, which you can then use to get the as***le to fess up and pay for fixing your vehicle. If confronting them isn't your style you can go all passive aggressive and put the photo proof on a "wall of shame" posting the incident in the break room for all employees to see.
BTW I'm assuming you aren't parking some huge crew cab truck in a economy car space.