If the driver of the stolen vehicle is not found than you will likely need to go through your own insurance company to have damages paid to be repaired.

State laws may differ but normally the person whose car was taken is not found responsible because they did not give the thief permission to drive the vehicle. Thus the car was out of the owner's control when it hit your vehicle.

If there is no liability on the owner of the stolen vehicle, since typically they are not held responsible for the acts of a thief in their car, their insurance company would not owe on the property damages claims of those affected by the person who stole the vehicle.

If you have collision coverage or uninsured/underinsured motorist property damage coverage you should be able to make a claim for the damages that occurred to your parked car by the stolen vehicle. If not, check with the law enforcement or state insurance regulator to see if there are any other means of getting your damages taken care of.