Why oh why. Sudden oil pressure drop.

I just installed a new WBO2 sensor and took the scamp for a quick ride. I took a datalog and oil pressure was great. I stopped the datalog as I was approaching home and noticed as I am pulling into the drive that oil pressure dropped to less than 2 psi. What could have happened with such a quick pressure drop? Tomorrow I plan to pull the distributor and spin the pump to check pressure and inspect the shaft before I start it up again. I can also install an analog gauge if I do not get pressure from the dash and efi sensors. Restarting the car for a few seconds repeated the low reading. My thoughts are stripped gear, plugged orifice to sensor. I recently changed the oil so the filter cannot be blocked. Which would strip first, the shaft going into the pump or the pump itself?