Well, I can't say it can't happen to me.
It seems you are in the habit of checking the chamber, which you did on the first two. Who knows what was going on in your subconscious as to why you didn't open the chamber that time.
This was a scary situation, no doubt. Definitely went a long way to reminding you for the future.
I've said before, we all assume guns in the cases at gun shops are unloaded, and yet if a store worker passes me a gun which he did not open the action in front of me, that's the first thing I do.
So far, I've done it every single time.
However, I won't say that the same thing can't happen to me in the future.
As humans, we are all flawed and things happen. Things will happen in the future too. There's no excuse for being human, but it is reality.
Had there been a discharge, there would have been consequences. We all shudder to think of that.
Thank goodness it didn't happen.
Take some solace in that we are all human. I'm more than certain, you will do your best not to repeat that mishap in the future and that's good enough for me.
By the way... I thank you for posting this experience! We all need to read it and know it can happen to any one of us. All it takes is a moments inattention or distraction.