Hi,
I think I've a similar issue.
If I go in the city of 2 of my neighbors, no matter what I do in their town (aid or not) when I go back to the world map they disappear.
As they are my southernmost neighbor I have no discovered area which disappear around them.
It only happen whith these 2 and it happened every time I go in there town.
To make them appear again, I have to move on the world map or quit and go back to the map.
Player Name: Liathary
World: zz1
Operating System: windows 7
Browser and Version: firefox 36.0.1
Flash Version: 16.0.0.305
Screen Resolution: 1366 x 768
Edit :
I've tried to open town of undiscovered people on the same line than the 2 who disapear and each time the town I've visited and everything to the south from this town disapear.
Maybe Extranjero's neighbor who disapear is on the same line too.
I'll try looking for it