Just getting back to the PC and a good look at your above pics. I don't think this is Gumaga. From what I can see it lacks the divided mesonotum and the metanotal sclerites are the wrong shape/size for Gumaga. The fact that you couldn't see the antennae makes me think they are right next to the eye. The rest of the characters also suggest this is one of the Lepidostoma and the case suggests pluviale group, which are very common in that part of the world.
I ran across [this thread on Roger's site](http://www.flyfishingentomology.com/forum/Replies_Display.php?t=0134) discussing with Kurt the identity of a larva fairly similar to this one. I keyed this one out to Sericostomatidae with the dissecting microscope (although I couldn't really make out the antennae at all), and from there it easily keys to Gumaga. I was uncertain in enough places that I was pleased to get to the end of the key and find cases that perfectly match this specimen.