The "lost" database is now available here:
http://restore.ultraguest.com
You may access your guestbook directly at
http://restore.ultraguest.com/view/[guestbook id].
If you take a look at your guestbook at the above domain and find messages there that are missing from your guestbook, please open a support ticket here:
http://www.ultraguest.com/support
Please include your guestbook ID or e-mail as well as which messages you would like to have moved to your guestbook.