If the pick-up tube wasn't tight enough it could of rotated down and been on the bottom of the pan. I guess I typed before I thought about it un-screwing, [in earlier reply]. That box on the end of the tube could cause it to rotate with all the vibration. I make a brace to support the pick-up tube.

I have seen the pick-up tube break off where it threads into the pump and fall off. I have also seen a piece fall off of the windage tray and block off the pick-up.

All of the bearings look starved for oil, so something cut off oil supply.