That is a good possibility that " Post Hole" has mentioned, I have seen both scenarios in the past. lean ran engines have a habit of expanding more which will allow the liner to rotate, and the baffle disk in some mufflers to to become pinched as the body cools. Some guy's pull the disk and toss it in the drawer.

One other possible cause is a wrist-pin clip has lodged between piston and sleeve, But not likely due to it turning over without plug installed.

Dan Z