Ok, saw this too. Stash is sorting two hand weapons improperly and sticking them in weapon and shield category. My guess is when its equipped on your inventory it takes those two slots, so it shows like that when it sorts.

The sorting of the stash is relatively a new feature. Before it was everything all over in one stash. Its a minor bug, I am sure they will get around to fixing it.

STS, great job so far bringing organization to the stash, I found a handful of items I didn't know I had still