I rebuilt my vacuum pump just 300 miles ago with sealed bearings.

I started to hear a noise so I popped it off. The bearings are gone and the pump is toast. Bearing races are still in the piston arm and on the roller axle

I haven’t dropped the oil pan yet to look for additional damage. Engine was still running when I parked it…

I’m trying to figure out how this happened. The pump was clean and dry inside. Is it supposed to be lubricated with oil pressure?