poppahymen,
While I can't speak specifically about the main gearbox in question, in general, anytime a main gearbox is run under loss of lube conditions it should be taken out of service and overhauled. Critical components like gears, sprags and bearings will likely need to be replaced.
Gearbox components like gears and bearings are designed to sustain 30 minutes of operation under loss of lube conditions without structural failure. But that does not mean they are fit for service after just a few minutes of operation with loss of lube. Gears can sustain scoring damage with less than a minute of loaded operation with inadequate lubrication.
riff_raff