In all honesty I wouldn’t worry too much. He’s hardly a hardcore rebel if he’s still getting a lift home with his girlfriends parents ( not exactly a weekend of carnage).
If it’s taught him a lesson, and nothing bad has really happened let it be.
Silent disappointment may be the best course of action. If driving lessons are coming up you could find a way of making him earn them back.
It’s tough with children, I find the values we instilled in early childhood are at odds with later life. In primary they’re taught to be humble, kind and respectful. Come secondary school and writing cvs, they’re to told to sell themselves, let everyone know how great you are, killer instinct etc.
You don’t want you’re kids to try drugs etc but you don’t want them so wet they don’t want to experience the world. It’s a no win situation.
To me the key thing is they respect me and can always talk to me. That way I can always help and influence them.