Step back folks, I got this one. I am a expert family therapist.
I can prove that you must be a decent father just by using a few of your own statements...
Ok first off you claim the kid was going to stay with his aunt. That simple statement speaks volumes. The fact that a 17 year old kid would even agree to stay with aunt Ethel is quite profound. Hell when I was 17....
Second the fact that the kid has his own car (STILL) and hasn't trashed it, lost his driving privileges or got so many tickets he can't pay them all, further speaks to your abilities as a Dada!
Third, and this is most important to us here on PFF. Your car made it in one piece. This clearly demonstrates that your offspring has respect for other peoples stuff. He didn't hammer on your car, that we know of. He didn't pick his little butt buddies up at the mall and mash around town doing reverse brodies. He probably wasn't out behind Home Depot or Wal Mart smoking dope and drinking with the other misguided youth.
Don't feel guilty for demonstrating a very valuable life lesson to your child. Respect other peoples property. Too many times we see youth today out destroying other peoples stuff. Smashing car windows, spray painting on walls, car shopping for pocket change to get a pack of butts. It just goes on and on the crap that kids are pulling these days.
You sir have done a bang up job IMO. The kids not so bad I bet. And if this little excursion is any indicator I would say he is well on his way to being a productive, responsible young man!
Keep up the good work! Oh and BTW I am not really a therapist but I did stay at a holiday inn express last night!