I've used the "search for survivors" guardian power and created "find survivor" missions, but how do I actually find the survivors? Do I just have to search everywhere and hope that I run in to them? Is there any sort of map indication of where they are?
As with any mission, you have to go into that patch of the map (press "E" when you are on the tile) and have to find the entrance of the mission. Then you can rescue that survivor within that mission. This is normally done by escorting him out of the mission alive.
Those missions are also offered normally, without using any scrolls.