For all those shafts to be stripped, he'd need a ton of power and pure luck. I'm banking on a diff pin that broke or the roll pin allowing the diff pin to move and carve those strips off the diff cover housing. there'* really no other way those could all be in the pan unless a different part was shaving the case.
The parts you mentioned should have gotten caught in the VB
and it'* baby filters from what I've heard about fluid flow paths. Although I will say, I've never looked them up specifically and could be wrong on that.