Ok, Fredericktowne Triumph says there is no washer for the axle (Bike Bandits microfiche also showed none). Indeed, all of the America/Speedy's and one customer America in the shop also had no washer. There's no Triumph part number for one, that's for sure.
The parts guy wasn't surprised and says Triumph does odd things like that between bike years.
He says no way it's my axle coming loose. He blamed the RK chain. Neither him or the shop guy like the RK brand, they use DID only.
I guess I'll monitor and send it back to RK if necessary.