Strange but anything is possible. Since it was jammed past the slide lock, we can rule that out. I doubt this is the issue, but pull the slide and check the front of the stopping block for damage and the bottom inside front of the slide. My guess is a piece of brass, off the shell casing, got lodged in the rails, and held the slide open. The extractor claw might have ripped off a small section of a weak area on the rim. Not likely but what other reasons could have caused this condition. A possible binding recoil spring, but that would not likely have held the slide at the fully back position. Upon forcing the slide forward, whatever was lodged in the rails was dislodged and the gun went back to function as per normal.

Bob