Brachycentrus (American Grannom) is a tube case maker, with an elongated 4 sided grey-black case.
More likely it was Rhyacophila (Green Sedge) They are the most common free living Caddis. The adults range up to 16mm in length, The wings are mottled shades of green and brown, the bodies are shades of olive (darker, early season, lighter as summer progresses.), Legs are various shades of brown.
Free living caddis larvae must have relatively fast moving, well oxygenated water, being the least advanced, they lack highly developed gills.
In most cases the Pupae will emerge in May or June, Adults may live for weeks. Adult dry imitations may be less effective than adult wets or emergers.
The pupae emerge from the larval habitat (riffles), rise to the surface quickly and break through the film to take flight almost immediately. Rises to emergers are violent splashes and often take fish airborn in the pursuit.
Egg-laying females crawl or dive to the bottom of riffle areas, paste eggs on the rocks and then simply let go and drift with the current until they reach the surface film and then break through slowly if at all, sometimes drifting for long distances, making a fine target for trout holding below riffle areas.