Without reinstalling? uh.. that could be long and hard.
check if you accidentally moved or deleted the folder FeralHeart\media\terrains
Inside It should have a folder called fhmaps with the 12 Game maps
also a folder textures with the terrain textures
and also a folder WaterMill and a file WaterMill.map
I don't see how installing a map could cause this, unless you required to place files out of the exports folder.