How do you get your triangles and lines back on a terrain model if they disappear when changing the feature definition or the element template.

I am not sure if there is something wrong with the terrains I created or what,  I have used this method to clean up the edges before and it worked fine.  But not it seems like I cannot select the terrain and when I change the feature definition or element template all the lines and everything disappear and I cannot get them back at all.

I doing all of this to clean up the terrain lines that are out side of my boundary in the few areas.  I am trying to use the insert vertex way of cleaning up the triangles I don't want.