They gotta check the cellphone records, I bet the girl driving was on her cellphone and hit the guy.
But lets not totally write the motorcyclist off free and clear from this. I know that guy was hella pisd especially when your life is endangered by two retard drivers. BUT it takes a guy with a bit more nerve to follow a car all the way home instead of just getting the license plate and reporting it right away. I think he was looking for a little more than insurance information. He was probably looking for trouble and he found a bit too much.
That being said the old man shoulda had a baseball bat or an angry right hook instead of spineless pistol.