If you can add in about how long ago this was and if you know whether it was a current or dead thread (as in if it was active at the time you were looking at it or it was years old) that might really help. There are not too many real world locations done on here since most of us are making maps for game worlds so that should help. Of course, if it's not really a map of Eastern Europe that bit could throw us off. If was a post holocaust type map that also narrows things down quite a bit..I'd start with Sapiento or Diamond since they seem to do the bulk of those lately. Also, searching for "watercolor" if the words were used in the WIP thread will help.
Again, if you can give a range of months around the time you viewed it that should help.
Anyway, welcome to the guild it's a great place to get your map geek on!