The recipe was a quest reward of Wild Hearts which was removed in Cataclysm. The recipe was not BoP and the quest was not restricted to alchemists, so prior to Cataclysm you'd see this recipe fairly regularly on the Auction House. Alliance players had to roll a Horde alt, complete the quest, and transfer the recipe to Alliance-side via the neutral AH. (Or, they paid someone else to do it for them.)
There is no replacement quest, so the recipe was effectively removed from the game. It can only be acquired from players who held onto the recipe. Expect to pay thousands of gold.
Also, Discolored Worg Heart has a really, really crap drop rate now. Not good for skilling up Alchemy.