After the flat tappet cam wiped out all the metal is in the engine, it's in the oil galleys and it's very fine pieces of metal they get in the lifters and wedge the piston and it just keeps pounding down till it hits the bottom of the lifter body. Now you have a collapsed lifter there will be more to come I have seen it happen more than once. When the second guy fix the motor did it get completely disassembled and cleaned and cleaned and cleaned.
Take the lifter apart and I bet there is metal in every lifter
