2001 Ford F150 Valve Cover, missing part
 

Just to the side of the oil filler tube is a small round hole in the valve cover about the size of a quarter? I don't see another part that appears to have come loose from it. It's dirty around the opening like it's been missing for a while. Might even be a 'cap' missing but wondered what it would cap and the purpose of the opening. Truck seems to be running okay. Is a 2001 Ford F150.https://cimg5.ibsrv.net/gimg/www.f15...89814e09ad.jpg
The hole to the right of the filler tube.

probably the PCV valve

Agreed.... I guess this is a 4.2 liter we are looking at?

Yes sir. 4.2 .

UPDATE...I found what does look like a PCV value hanging down below as if it fell off at some point and plugged it back into the open hole at the valve covers but it's not connected to anything else at the other end of the approximately 12" tube extending from it. Where does the other end go if anywhere or does it just vent?

It should plug into a vacuum port somewhere. Mine is not a 4.2 though, so I am not familiar with where the hose ends up. Maybe these two users can help....

@BareBonesXL @kd4gij

They should be a better help for you on the 4.2

Well it is pouring out right now. When it quits I will go out and look

Final Update: As luck would have it...I live in a small rural southern town full of farmers and mechanics. I was looking under the hood and a man walked up and said, "What you looking at?" I told him and he reached over and plugged the other end up under another part nearby into a small port-like opening and said, "There ya go." LOL I felt dumb and relieved all at the same time. Honestly, I would never have seen that little opening under the area where he plugged it up.

I think a recent oil change may be the culprit. It would very easy to bump that part and pop it loose from where it lives.

Thanks for everyone's input. It helped. I appreciate it!

Lol, you can see it at the right top of your photo. I would of did the same lol.