"The people standing around and watching me think that I'm writing down my name and phone number."

As opposed to him simply disappearing? Sure, him putting down a note keeps other witnesses from reporting *his* ass, but if the city tow truck lead fails, the first thing they'll do is ask local body shops if there are any leads. If the only person who "saw the thing happen" happened to bring his car in for repairs, don't you think that raises an eyebrow?