If we are to engage in searching for the missing one night stand and her bodyguard, Gib will suggest returning to the Shill and searching their room over quite thoroughly for any signs. Kith would be highly helpful in that regard. From there, the idea would be to check out all of the possible exits from their room and the building. If there's a stable and stable master, check to see if they had horses and if those are gone, when they took them, etc.
Gib is absolutely positive that the pair are involved in this whole thing in one way or another and until the party either concludes their story or exhausts all possibilities, he'll press to follow that path.
He'll also admit that there's a strong likelihood that the Death Cult has something to do with this as it is less likely that the targeted wizard's notes about such a thing and the assault on Crandel by undead are coincidence than that they coincide. He's seeing possibilities link up left and right, and to his ordered mind, there's a method for building out the trestleboard and unraveling this puzzle.
"If we figure out what happened to Davena and her man, we'll likely figure out more about the Death Cult that Athandar was researching which is likely behind the undead uprising (that just makes sense to me)."