That's a great story. Similar thing happened to my wife about a month ago in Kent. Saw some kid and his buddy side swip a guy while trying to turn into a fast food place and then take off. Police came and she stepped in as a witness and gave a description of the car. When everything cleared up and the cars left, she looked into the street (dark, rainy night) and saw something. She walked out there and found....the kids crumpled license plate with the other car's paint on it!!! I wanted to go down there and wait for him to show up looking for it but had something more important to do (could have been priceless). The police looked the car up and it matched her description of the car exactly. I had a good laugh when she told me the story and then pulled out the plate to show me.
Hitting a Mercedes is not worth going to jail over. Even if you don't have insurance the worst that could happen is a HUGE ticket and a suspended license. Now he's just some punk in 6-wing who owes a ton of cash and has no license.