pictures again. It is melted on the top above the compresion rings. The rings didn't break. They still held compression like the other pistons did . How would pieces of the piston get in the oil? It would have to go past the skirt by your observation? Maybe it took a short cut through the valves, past the valve stem seal and then down the oil passage into the pan from the head . Must be some magic pistons JUN is selling if that is the case.