Meaning, not the one where it gets messed up with the words of power for Marked for Death... but I figured I'd post it here, since it is a Dawnguard shout.

In my game, all of the (correct) words of power for the Drain Vitality shout have vanished, and the shout (appropriately enough) became grayed out. Clicking on it reveals the prompt, "Dragon souls are needed to unlock shouts;" note that I have 16 unused dragon shouts in the bank, so to speak.

This happened at some point after installing Dragonborn, but I'm not sure when because I wasn't using my shouts other than the couple I have favorited (Drain Vitality not being among them obviously).

I play on PC, all the official mods and unofficial patches installed - and up-to-date, at least as of about 2 weeks ago. It may be that one of the unofficial patch updates was responsible - again, I'm not sure when the shout got glitched. For the record, here's my load order:
high res text pack 1
high res text pack 2
dawnguard
hearthfire
dragonborn
unofficial skyrim patch
unofficial high res text patch
unofficial dawngurad
unofficial hearthfire
unofficial dragonborn
sylgja (a mod that swaps sylgja's miners outfit and pickaxe for a farmer outfit and dagger, nothing more)

Being on PC, I tried the console commands for teachword and unlockword (2008a63, 4, and 5) but it produced a new entry for the Drain Vitality shout, without removing the old one, and also skewed all my journal stats regarding shouts. I also tried the removeshout (20018244 and 200181b8) command recommended for the more familiar Drain Vitality bug, but there was no entry found for those codes.
I think my shout counts got screwed up whenever this glitch happened (I show 81 words of power (WoP) learned, 84 WoP unlocked, 29 shouts learned, 28 unlocked, and 27 mastered, despite having learned and unlocked all - I should only be off by 1 shout learned (from my brief stint as a lycanthrope)) - point being - enough stats are glitched in this game anyway, I don't care about them so much as I'd like to either completely fix the problem, or at least delete the blank Drain Vitality entry (and then I can console in the appropriate shout and damn the stat accuracy).

Whew. Any advice?

Thanks.