It depends when the items were stolen and why the car was impounded. If the items were stolen while under the possession of a company or the city, I would feel they are responsible for the recovery. If you have a renters
policy your items may also be covered on that. See more about renters insurance and theft here.
Car insurance doesn't cover the contents of your car, only if your car was damaged in the process of the theft or stolen entirely. If you have any other questions, don't hesitate to ask