Confession is good for the soul, so I am told. I made a similar mistake with my Ed Brown EE. A 10mm round made it into a bag of 45 acp and was loaded in a magazine.

The 10mm round feed, chambered and fired. It didn't eject and was therefore, discovered. The round, when it was fired, didn't "feel" right.

The case was, of course, split for it's full length. The pistol was field stripped and no sign of damage was found. I have always been careful in my preparations and when shooting but, the take away from that experience is to check and double check. Then check again.