Piston pin bad ?

Assembled short block several years back . Coated holes and pistons with wd40 and bagged it up tight. Just did cam , valvetrain and heads a few months ago . All new parts.

I would agree that it looks like something was bouncing around in there but how did it get in and out without damaging the valve face or seat ? I think what we are seeing on the chamber and valves are from the piston pieces flying around.