Legal Question in Real Estate Law in California

Sure, but if you lent it to someone, it's likely the police will tell you it's a "civil matter" and you will have to find it yourself or hire a private investigator.

The longer you wait, the less seriously your report will be taken when finally made.

It is possible to commit theft by false pretenses, i.e., you don't have to be carjacked at gunpoint (robbery) or have it taken from your possession sneakily (larceny). If someone asks to borrow your car for a week, but at the time of asking has NO intention of returning it, that's also theft.

However, if someone borrows your car with your peermission, intending at the time to return it sooner or later, but fails to do so, that's a civil matter.

By the way, vehicles are not "Real Estate and Real Property" and this question doesn't really fit the category it's asked under. You might re-ask under a personal property, motor vehicle or crimimal law category, adding more facts about the circumstances, if you want a better answer.

What's more relevant is who is on title-registration, and who has permission to use the car.