The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
But the body was not segmented.
It's probably a Tipulidae (Crane Fly) larva. The lower Owens is the wrong habitat for rhyacophilids (Green Sedges). The specimen sounds too big for the hydropsychids (Little Sister Sedges) that low in the system.