As I recall from the other thread, this young man is a combat vet and, from the sound of it, also a CCW holder.
He's used to guns, being around guns, wearing guns, carrying guns, cleaning guns, storing guns, etc. It's becomes way of life. Second nature. Just another thing, except it's a very important thing, to be sure.
Traveling, going to different places, things are different and the daily routine is interrupted. Train of though is interrupted. Things normally done get pushed aside.
Add to that the wife. Any time I'm doing anything important and the wife starts talking to me I have to stop everything I was doing or I'm going to mess it up. When she stops talking, I figure out where I was and continue the task. More than once she has caused blood and injury when she interrupted me.
The kid should have kept it together better, no doubt. If it were me, would I freak out and go overboard as have several in our audience? No. I live a slower life and try hard to remember where my guns are at all times, but I've had to go back downstairs and get one before I went to bed. It happens.
If it happens too often, though, it would be time for a rethink of a persons life and habits.