You will still be able to see it if you look really hard. Even if it was touched with paint and oversprayed, wait till evening and hit the area with Brake Cleaner. It will come off like nothing. The Blue paint will not wash away first because it's embedded and you will have your answer.
EDIT: My wife parked this weekend and when we came back there was a big truck that was 11" from her car, I told her to check the door and surely, there was transfer, She takes such good care of her car and I could tell that she was truly hurt inside. I pretended to check it out and then sucker punched the truck with as tight a fist I could.
Sorry to the owner of the turck, but you are a total **** UP and desreve twenty fold what I did to your vehicle. If you hurt a car, LEAVE YOUR NUMBER, not because you want to pay to fix it, but becasue you SHOULD own up to your mess.
The worst thing is that he didn't even move the truck, he just walked away.
(braindead(braindead(braindead
P.P.S. Ouch, my ******* hand hurts.