hit a car at a parking lot?

today at school i pulled into a tight spot and hit the car on the right side of my car and there was someone sitting in the car in the left side. i am a new driver and i sat there and hopefully waited that the owner would show up but never did. the person next to me got up and left there car. when i got out of my car to look at the damage i saw that my car's paint(which is white) scraped off and the other car had my paint on it it already was taped up from a previous incident. the car was black and it already was covered in white marks all over the car not just where i scraped it. the black car didn't seem to have any new harm done on it.

i decided to leave and go to class and i spoke to one of my friends about the incident she told me to go back and leave a note with your contact information. when i went back to do that the car was gone and i was going to report it to the security office but my Friend told me to leave because if the person drove off and then they pro bally didn't notice anything new. but i still feel guilty about not leaving my information. Even if there car was not damaged i still feel bad