I am having an issue with the Dawnguard quest "Prophet" where the play is tasked with capturing/rescuing a Moth Priest (in my case capturing as I am playing the vampire side of things). Upon reaching where he is held in Forebears' Holdout, before looting or attacking anyone, my quest log is updated to say "Deactivate the magic barrier" and a quest marker is placed on Malkus' corpse at the feet of a Dawnguard and a named Dawnguard "Vanik." After doing some research I've found out I am supposed to kill Vanik, as I have, and loot the Weystone Focus off of his body and take it up to the Weystone font above the magic barrier. Unfortunately, Vanik does not have said Weystone Focus, neither does Malkus and neither does any other NPC/Enemy in Forebears' Holdout. I've tried going back a significant way in my save files to try to rectify this and nothing seems to work. Also I have tried exiting the instance and re-entering with no results. Any suggestions?

Start Dawnguard over again

That's what I was afraid of. Any suggestions that don't involve me shooting my progress in the foot?