My thoughts exactly Richard, I all this made me take the cover off and have a look at my pump today, happily all OK!
I pulled off the gear so that I could turn and check the pump, it took half a dozen slow turns to prime (it was driven four days ago) and squirt oil out of the jet that lubes the thrust bearing, rear roller bearing and pump gears,
Without this jet the pump gallery would soon drain dry through the bearings when going down hill, or parked on a slope. The front bearing seems to be lubed by oil thrown off the crownwheel, this cannot happen to the rear one. Pioneers must have a catcher for this, or summat.
The worm and crownwheel could probably last a long time running light just on what is dragged round from the sump, but the rear bearings must surely wear or fail quite quickly, and these takes all the thrust.
Running pumpless, especially if particles from damage have wrecked it, must be a bit chancy, it's there for a good reason after all!
Nearly forgot, the pump definately does not work in reverse...