While it is very unlikely that anyone is going to be going through your vehicle, it is possible that there may be a random inspection, dependent on the route the truck is taking. While this shouldn’t be any problem at all, some folks might wonder about this if they have personal belongings in the car when it is shipped.
In the unlikely event that your car does get searched, you shouldn’t have anything to worry about unless you left something that the company is not allowed to ship inside the vehicle. If all you left in your car is everyday personal belongings, then you have nothing to worry about.