This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
After camping atop the Gravelly Range and mostly dodging thunderstorms throughout the day, we set up to camp in the evening at Cottonwood Campground along the upper Ruby and drove to fish a nearby reach that looked good on Google Earth. There wasn't much visible bug activity and I didn't see a single fish, but I did manage to find five small to medium rainbows on nymphs and soft-hackles.