Legal Question in Real Estate Law in California

Why would they?

Well ask them, then satisfy whatever their rules are.

Towing companies operate under rather strict and comprehensive laws and rules regarding all aspects of the business, including release of loose property in towed vehicles. When you say "the car" instead of "my car," this suggests that you aren't the registered owner. Maybe the towing company cannot give the property to anyone other than the registered owner of the vehicle. Another possibility is that the towing fees have to be paid before you can have access. As Mr. Nelson suggests, ask the towing company.