It happened to me also recently, but I didn't hit anything. I was going through a bit of a rough patch of road, but I didn't feel the impact of going over a significant hole or bump and the hood popped. The dealership found some scratches under the front bumper and assumes that's what caused it.
I'm exchanging emails trying to get more details about the incident: exact speed I was driving and how the system is supposed to work (if there's a speed from when the system activates) etc.
Some years ago I hit another car from behind and the pop up hood warning came on, but it didn't actually pop the hood, and that time the front bumper was cracked, so I'm a bit "flabbergasted" at my situation.