Who do I sue?

My vehicle was in an accident, my insurance company sent it to a collision repair company. The insurance company total loss the vehicle and gave me the option to buy it back. When I went to pick the vehicle up, about $2,000 worth of equipment was missing and it was not broken into. When I brought it to the Collision company attention. They in turn told me I signed a I guess a release but when I read the release the piece of paper I signed, says I acknowledge that I have removed all unattached personal and valuable articles from the vehicle I understand that the collision repair company will not be responsible for any belongings left in the vehicle. My stereo equipment was uninstalled. I called the police to make a police report. The manager gave officers that piece of paper and also told me it was a silver matter I asked them to check my vehicle because the items wasn't stolen they were uninstalled. The insurance company told me it would be a death claim with a deductible. Who do I sue