+Rep for JailBird, that's some good work there dude.
I'd lay of the vigilante justice really as it will be obvious who was dishing it out- just pass the info along to the police as quickly as possible and make sure they act on it.
That is pretty cool how this forum works when there is a problem to be resolved. You know if there is one place where you can find at least one person who has some kind of knowledge on anything that this is a great place to dig in. So a red 2008 Mustang with a missing passenger side mirror. That should not be too awfully hard to track down. Like stated I would provide this information to the Cops straight away so they can get going on it. Then if you know some of the body repair shops in your area contact them and explain the situation so they can keep an eye out. Plus be very attentive in noticing red Mustangs driving about in your area. I bet you may just see this A$$hole again, and you can follow them to home or work and report it. Hit & Run carries some pretty heavy penalties in most states. Especially considering the nature of this incident where he just left you laying on the side of the road. Good luck with catching this idiot.