I lost a password for a page in a password protected Calc document. how can I undo the lost password or save the rest of the document??
To remove the protection from a sheet without knowing the password, you need to save the document unprotected, and to manipulate the file with appropriate tools. That’s not difficult as the protection is weak insofar, but it’s rather difficult to describe since some details depend on the software tools you use.
(I can do it for you if you find a way to send the file [unencrypted!] to me. You may register to forum.openoffice.org/en where I als contribute. There real forum software is used allowing for personal messages.
(If this is also about the password needed to open the document: Forget it.)