I'm not quite sure I understood your question right. Could you clarify whether you have access to the console that granted the right to mount?
sudo privileges can be revoked with
-K The -K (sure kill) option is like -k except that it removes the user's timestamp entirely and may not be used in conjunction with a command or other option. This option does not require a password.
-k When used by itself, the -k (kill) option to sudo invalidates the user's timestamp by setting the time on it to the Epoch. The next time sudo is run a password will be required. This option does not require a password and was added to allow a user to revoke sudo permissions from a .logout file.
This won't work with gksudo.