When waiting, NPCs can go where they wouldn't go normally.
While waiting in Seyda Neen on top of the tower, I noticed that after waiting, one of the NPCs was in the place between 13 and 14 on this map: http://www.uesp.net/wiki/File:MW_Map_SeydaNeen.jpg - the place where you find the Fargoth's ring in the barrel. As far as I know, there is no way to get in there normally from the outside, and no NPC would ever go in there. I guess the NPC was Indrele Rathryon.
(RM-2981 from redmine: created on 2015-10-27 by Mateusz Malisz, , closed on 2016-04-12 by Austin Salgat)