Your dead on. Upon further inspection I found the cam damaged as well . The lobe was worn considerably. I unfortunately am not always up on things like the low zinc so it bit me in the ***.
I was thinking about it because zinc is or was added for scuffing or sliding action, such as rocker arms against valve tips or valves and guides and it suddenly hit me that the lifter plunger and body is the same fit. Maybe there's something to it. Maybe not.
