State laws and insurance differ but in general unless the at-fault party is found, the one who stole the vehicle from the dealership and hit your parked car, there is really no one in which to go after for the damages to your vehicle. If you had collision coverage on your vehicle you could have made a first party claim with your own insurer but with only liability coverages this is not possible.

Normally for the owner of the vehicle, in this case the dealership, to be held responsible for damages sustained to your car, they would have to have given the driver permission to operate the vehicle. Since a thief was operating the dealership's stolen vehicle obviously permission was not given for the car to be used and thus usually the dealership (and their insurance carrier) could not be held responsible for the thief hitting your parked vehicle with their stolen vehicle.

State liability laws differ though so you want to check with a lawyer to make certain what the owner of a stolen car can be held liable for in your state. To get consumer information and see if there is any state fund that may provide you help with this situation try contacting your state's insurance regulator.