Rescuing Lob from Brittleshin Pass

[pemmons1]

I was going to inquire about this but finally found the answer, so I'm just giving it as an obscure piece of information.

A quest given by Dawnguard was to rescue my "friend" Lob, kidnapped by vampires, from Brittleshin Pass, where they were keeping him prisoner. I killed all enemies there and retrieved all loot but could not find Lob. Finally I tried the clairvoyance spell to complete the quest. It seemed it was taking me all over the map, but finally led me to my castle in Ivarstead (the Thane of Ivarstead mod) where I had stationed him as a follower (My Home is Your Home mod). As soon as I talked to him, that part of the quest completed.

I don't know whether this peculiarity is due to one of these mods (incidentally, the Thane of Ivarstead mod seems to have disappeared from Nexus; if so, it's unfortunate.) or whether it can happen with similar radiant quests from Dawnguard, but it is one of those innumerable little quirks that a player must keep in mind.