Nevada 750 93 reg

My son in law was removing the barrels from the engine on a 14000 mile machine - looking to do a full rebuilding and custom. When removing the pistons he found the second ring in the left piston was shattered into small pieces within its groove. The pieces just fell out on removal of the piston. I’ve inspected the barren and piston and all looks ok and there is no sign of scoring. Just wondered if anyone had every seen anything like this before. I haven’t.