Machine shop forgot oil plug?

I hired them (amongst the other machine and cleaning work) to remove and replace the cam bearings and freeze/oil plugs. I don't have a cam bearing tool so this made sense, but in retrospect I should have just done the plugs myself - I ended up having to pull most of them again anyway to actually flush the block out properly after I got it back.

It seems from the diagrams that if the plug weren't installed at all, I would be able to see from the oil pressure sender hole clear to the other side of the oil pump hole on the main bearing cap, yes? If so, then it seems there is, as krazykuda said, a plug installed possibly upside-down. I'm guessing that the protrusion of this upside-down plug into the oil filter hole as shown in my third photo would affect my oil volume since it obstructs the hole slightly?