When the Shattering came to Azeroth in 4.0 many vanilla items were taken out of the game and making them unobtainable, this enchant amongst others:
Formula: Enchant Weapon - Icy Chill - Item - World of Warcraft
So naturally collectors would pay top gold for such recipes.
Well, 6.0 readded this item and not a lot of AH fiends have caught up to that fact.
It drops from the Angushied Highborne that spawn at the northern part of Lake Kel`Theriel in the southern part of Winterspring.
They share a respawn timer with the ghost, so just kill all of them and loot them, takes around 5-10 minutes to farm up the recipe.
It also helps if you upvote the comments on wowhead that say that the item doesnt drop anymore so its the first thing people see when they check where to get it.
Bonus points for selling if you advertise it in trade chat on some 45-60 vanilla toon that "just resubbed" and is cleaning out his "bank".