I have a number of templates where a rogue developer has locked the design and has lost the templates (or won't share them).
There is a solution to unhide the design.
1. Make a local copy of the database
2. Ensure you have manager or designer rights.
3. Open up the .nsf file in a hexadecimal editor.
4. Change address 000000BC from the hexadecimal code 20 to 00.
5. Save the .nsf file.
This does not seem to work with 8.5.1