Well the car could have been under salt water for ten years, hit by a Greyhound, lifted and moved 100 miles in a tornado, or hit with a shopping cart at the Big box store! Even hit and run while parked at an end row in a motel parking lot!
I tried doing an on-line chat at CarFax to ask the question, but after 7 minutes of waiting for a rep, I got tired of waiting.....
Just because it's not on Carfax doesn't mean it didn't happen! As far as their listing of "minor damage", it all depends on who did the reporting. I'd imagine that, despite whatever their official answer to you query might be, it could be anything short of totaling the car.