Brain Freeze Missing

Okay, I may be an idiot (probably am). On my lvl 85 frost mage that I haven't played forever I cannot find the brain freeze spell/icon in my spell book. Yes I have the necessary talent selected and points assigned. I did convert the toon from Ally to Horde but how could that affect a spell?

Any suggestions are welcome.

Thanks
Brain Freeze is a talent/proc that modifies the way frostfire bolt and AM interact (AM stops proccing, BF does). Not a spell in its own right.

It is on teir 4 of the frost tree.
Thank you, I did not understand that. For some reason I thought it was a spell. I appreciate your helpful reply.
Anytime!