I purchased two ascended insignia recipes from the Guild Commendation Vendor in the Guild Hall. They appeared (as expected) as a stack of 2 in my inventory. I double-clicked the stack and chose (what I thought) was my first recipe. In my case I chose the Sentinel recipe. Instead, the result was my stack of 2 pick-your-recipes becoming a single Sentinel recipe. Obviously, I expected to still have an additional recipe left over to turn into another selection.
Edit: Nevermind, it appears to be an inventory screen redraw issue. Similar to the problem that appears when transferring items out of the Guild Bank. You drag it over and disappears from the bank but doesn’t appear in your inventory. Then you move a second item from the bank to the inventory and the first item magically reappears.