What version and SP of SW? Do you have your scanTo3D add-in enabled when you open the file?
I am using SW 2011 Premium with ScanTo3d enabled. It does show up in the feature tree but when I select it on the tree it does not highlight any part of the model.
Strangely enough, I tried to replicate this by starting over and now I can hide and show the mesh. Not sure what I did but at least now it works.