Knocked Car - Overthinking?

I was parked within my bay and someone parked their car over the front line of my space and their bumper was nearly touching mine. As I turned on the ignition, my car jolted forward and knocked their car. I reversed back, and had a look for any damage and I couldn't see any, so I drove off. Im now overthinking the whole thing and wondering whether I should have left a note or taken a picture or something? I don't know if I did the right thing given that there wasn't any damage. Here's an artistic drawing of how the cars were parked