I would guess that what drops from Blingtron would be the pet rather than the recipe. I know I received the Mechanical Dragonling once. Of course the best way to make sure it drops from Blingtron is to buy one off the AH. Then you'll get it right away
The comments on Wowhead pretty much tell the story. A couple of players submitted tickets and copy/pasted the responses. http://www.wowhead.com/item=21277/tranquil-mechanical-yeti#comments
I'm guessing it wasn't removed from the game. Probably a broken link somewhere that doesn't allow the quest to come up.
At any rate, if you're an engineer, don't waste your time on the quest (unless you just want to prove it's missing). And if you can make it, then there's no use in selling it cheap. I doubt they will fix the quest with a new xpac and all.