Deemzzzz - Thanks for your reply !
I tried the Ironforge trainer and Enchanting Supplies Vendor - but they didn't have it. It's the Skill 20 recipe I was looking for. I have the Skill 1 recipe. It's no biggie but I like to have all the recipes and formulae even if I don't use them. I'm not sure, but it may be one of those recipes that Vendors have in 'limited' supply. I guess I'll just keep looking.