Help!! Accidental hit and run not knowing of collision at the time.

[a10090]

The other day, while searching for a parking spot at my schools cramded parking lot i must have barely backed into someone. However, i wasn't aware of it at the time. It happened when i was going down the lanes of the lot and all of a sudden someone starts backing out of a spot. Knowing that i was
kinda in the middle of the way, i backed up a few inches to allow him through but while i was doing that i must have bumped the guy behind me. Of course, me and my passenger did not notice any impact what so ever so we didnt bother to stop and talk to him. AN hour later after i parked, my friend who happened to be near the scene at the time, tells me that i backed into someone and that the person wrote down my license plate number. The whole rest of the day i tried to find the guy whom i accidently hit but had no luck. I later noticed a few small scuffs on the back of my car.
Although i technically committed hit and run, i had no clue at the time and since the guy has my plate number, i know im screwed.
Does anyone know what the offenses and or punishments for this are? BTw i live in Illinois. Also does anyone have any advice on how to evade
this awful situation or how to win this in court? Help would be appreciated!

[msgny]

Your passenger could give a statement or testify that you did not feel or hear the bump--if that is true.