The shop should be liable unless there was a hold harmless agreement. If your car was damaged during a criminal break in at an auto body shop, and you did not sign such a release, you probably won't have to pay for the damages to your vehicle. In general, auto body shops and automotive garages are required by law to have liability and loss insurance on their property that will cover the vehicles that are being stored and repaired at their facilities. Much like the question you are asked by your own car insurance company about where the vehicle will be stored and whether it will be garaged when you make changes to your policy, auto body shops are also required to provide information on their facilities to the insurance company that underwrites their policy, allowing them to gauge the risk of theft, fire, break in, damage, flood, or other destruction.
Hold liable or hold harmless?
You will need to discuss the auto shop's insurance policy with them to find out what all it covers. You will also need to determine the specific state law regarding these liability issues. The rules can vary depending on the area and whether there was a hold harmless agreement that was signed. In fact, some states only require that shops post a sign saying “we are not responsible for theft or loss of property for vehicles left at this location” in order to avoid liability, even if you did not sign a specific hold harmless agreement.
If there was no hold harmless release, nor a sign disclaiming liability, then you may be able to take the auto body shop to court if they do not agree to cover the claims through their insurance. Be prepared to prove that you didn't release them from liability, and be prepared to show how much it will cost to repair the damage. You may also wish to have a lawyer working for you to make your claim or file your lawsuit in order to have the best chance of successfully being reimbursed.