Took my oil pan off today and found this

[FRED]

It helps to put a known size object in the picture with the item your talking about so one can figure out the size of the screw.

That screw came out of the pump housing. It was SUPPOSED to be staked in after the install of the screw. Someone did not stake it. The result is it vibrated out and fell in the pan. See attached jpg.

Oil jets can come out and they fall out into the pan thru the opening in the intermediate housing. That's how they would get in the pan. But that screw is the oil pump screw.