I finally got a response about that, after waiting for almost 2 days. There are some recipes that have the wrong LW skill requirement listed, so if you try to use a pattern you're not supposed to be able to learn, you get the "Item not found" error. It was probably stealth-added in a hotfix and they will fix the item description with the next client patch. Kinda annoying, since I'm stuck with Cloak of Beasts and Cloak of War as yellow for 2 more points before I get to the PvP recipes at 510. Current prices on my realm, it's 500g+ to craft either one, and neither are selling on the AH.