@Noobz - zoom his picture and it appears the pieces around round like wire. Possibly some kind of internal part of the oil pump like the relief valve spring shown below. It would be a stretch but just trying to come up with a way for something to get into the pump if the pickup screen is 100% intact.
The wire clip that holds the plunger in the lifter body?? That's the only thing that would be about that diameter with a round cross section,but that would bring about other issues I would think. Like stated above, I don't think it would make it through the pickup screen.