Yes, this doesn't happen very often, but when requested we have recovered or changed Joomla Super Administrator/Super User passwords.
Firstly if you have access to the email address that was used for the admin user, and you have made the "lost password" feature available on the front end, the simplest thing is to do is to use the "lost password" Front-end function. The site will send an e-mail to the user's e-mail address and allow you to change the password.
If this isn't possible then as long as you have access to the MySQL database using phpMyAdmin, the password can be changed, or a new Super Administrator/Super User user can be added.
If you are locked out of your Joomla site and require assistance CONTACT US