TL;DR: missing shelter survivors don't spawn sometimes. Had it happen up to twice in some missions.
Not sure if this is a bug so I'm going to flair as discussion until this is either confirmed or denied as an issue.
Anyway, I've been doing a lot of low-level rescue the survivor missions as I'd like to get that 10k banner and I've noticed something lately; even on missions where I'm the first one loaded in, where not a single survivor dies, sometimes we'll end the mission with under 15.
It's not like I don't try to find them, I scour the map until every inch of it is visible. And yet, I'm never able to find the last survivors.
Just now I played a mission and it came down to one last survivor, which was one of the shelter dwellers you have to search and then a blue circle spawns on the map (in the same vein as Ned's medkits do). Thing is, when I searched the shelter, a circle didn't appear. Even worse is the fact that the second last fella was also lost but spawned in just fine.
So yeah, is anybody else having this issue?