I have 2 towns which doesnt have the townstone in the exact middle :3
But they dont have lost regions. One is in a pocket universe and one is in the new world(=66)
I'm talking about the region with the townstone in it, not the townstone itself.
When you place a townstone, you will place it in a region, that region will become the center-region of your town and it will always stay in the center.
But it is still possible to place your townstone in the very corner of a region and that will cause the townstone to be not in the center of your town.