If the car isn't stolen the owner should be responsible as its their car. They can eat the fine/charge or tell police/courts who drove it. If they can't trust someone to own up to their criminal acts in their car then they shouldn't have let them use it.

If someone let someone borrow their gun (not stolen, different circumstances) and then that gun is involved in a crime with no evidence of another driver what should happen to the owner? Are they responsible for their gun?