oil pump fail

I have been messin with cars since 1974. I have never seen an oil pump fail that failed all by itself. I am certain that it happens, but it's got to be extremely rare considering that an oil pump is the closest thing to the oil besides the pickup and pan. Long as there's a full pan, it'll pretty much get splash lubed just rollin the car around the yard. In short, I would not stop your investigation at the oil pump.