Well, at the same place you have also a drop down menu to specify the disk image location, however, that would mean that the path to the disk image changed, which should not be the case, unless you set the location specifically at the time of creation, or that the disk image which the folder should be linked to is not in the expected folder home/Library/Application Support/com.taoeffect.Espionage3/Data....
So first, count the protected folders in Espionage, record for each OK folder the disk image name, and see if you have one left in the aforementioned folder, if you do, then link this one to the problematic folder...
Let me know how it went.
Zsolt