Same issue here. I had completed the quest and learned the tome for this polymorph variant. I did not know there was an issue with Alliance mages not being able to cast it till I read the hotfix about it.
But after the hotfix I noticed it is completely gone from my spellbook. I ran a script and it confirms I completed the quest and I tried to cast the spell through a macro and it does not work. I submitted a ticket about this issue and was advised to fill out a bug report so I am adding my voice here about this issue.