This was taken from http://fplanque.com/dev/mac/os-x-sparsebundle-shows-up-as-regular-folder
What do you do if you have, say, an encrypted sparsebundle and some day you try to open it and you discover it shows up as a plain folder in the Finder instead as a bundle icon?
Double clicking will just open the folder and show you the bands that make up the bundle.
I’ve forgotten how to fix the issue, you can at least mount the contents of the bundle by typing this is the terminal:
Then you’ll have your virtual drive mounted on teh desktop, and if need be you can just copy them to a new sparsebundle.