When can I expect (if at all) to hear from other person’s insurance after minor at-fault accident?

A few days ago, when leaving an event, I was involved in a minor car accident when an emergency vehicle was attempting to leave a parking lot. I backed up to give the vehicle some space to move and did not realize that there was another vehicle directly behind me. I ended up colliding with that vehicle at about 1 to 2 mph,
given that I was backing up extremely gently just to give the emergency vehicle some as I was backing up extremely gently just to give the emergency vehicle some space. We traveled a bit further down the road, pulled over and my relative who owns the car I was driving swapped insurance information with the other driver. I do not believe numbers were exchanged. I surveyed the damage, or lack there of, and took pictures. I do not believe that the other driver exited their vehicle to get damage photos. It was a bit later at night and nerves were high, but from the photos it appears that no damage was done to the other vehicle. If anything it would’ve been very light paint damage that was not visible at that time. Police were not called and to our knowledge, no accident report was filed. We did not report this to insurance as it was extremely light damage and figured it was not worth any possible rate hike. The other driver was insured and traveling into our state from a different state. What can I expect going forward? Does this seem like a case where I can expect a phone call from either the other drivers or our insurance, or at worst case, a lawyer?

It is possible that the other driver let it go, but the situation does make me uneasy and afraid that I can expect a letter from insurance or a lawyer at any given time. Is this likely, or am I being paranoid? Thank you for any help.