Put tag in notify when found mode. Now , every iPhone that pings it is going to report an approximate location. And don’t be surprised that the location accuracy is off by a significant amount. But you will get hits all around the storage facility so you can be pretty sure that the car is there.
Then if the car is stolen and moved, you will start getting notices that will add up to car is stolen.
Now, you will have a short amount of time to act as Apple’s anti stalking algorithm will kick in and start alerting the thief (if they have an iPhone) that a tag is following them.
But at least you will know that the car has been moved.