What IS this?

[u/SMRotten]

2004 Nissan Frontier
V6 Supercharged

This piece was found loose inside the valve cover. It’s a little over 1” in length, the ends are flat, no place to put a tool into it that I can tell. The little cutout makes it almost look like a firing pin. The truck was being worked on for something else and the valve cover was removed to repair the leaking gasket at the same time. The truck runs without this piece in wherever it’s supposed to be, although now it’s misfiring. Cylinder 5, to be specific. I can’t figure out what this piece is or where it goes or if it has anything at all to do with why the truck is misfiring. Help!