No oil in valve cover?

Hey guys im new here and i really need some help here. I had broken a lifter in my mustang not long ago... I replaced the lifter and did all that, i had to adjust that rocker so now its off by a little bit no biggie right. Well i started the car with the valve cover off to see which rocker the ticking was coming from(to see if it was the one i was messing with). Anyways i was expected oil to hit me in the face but to my surprise no oil at all showed up... The only oil up there was the oil that was there when i started working on the car to begin with. What could be the problem guys? When i bought the car about a month or so ago i noticed at idle the oil pressure was VERY low but when i reved past around 2krpm it would shoot way up. Thanks in advance...

I replaced the oil pump and shaft, didnt fix anything. BUT while cleaning the pan i found a chunch of metal looked like a little cap. Found out later it goes in the lifter galley and plugs up some kind of hole. SO im thinking this is the problem, going to look into it tonight.

Aight guys cracked open the timing cover and i need some pics or somebody to tell me where exactly the oil galley plugs would go, i see a couple holes and im kinda confused on which needs ot be filled..thanks

Alright got that hole filled and the car back together, oil pressure is high and is lubbing the top end now. So happy thats all it was...