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.
These widely varied terrestrial insects sometimes accidentally jump into trout streams. I have heard of trout being selective to them, but it is not very common. Anglers often call them jassids.
They are very small and are best imitated on hooks sized 22 or smaller. They can be treated the same, from the angler's point of view, as the Membracidae family of leaf hoppers.