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Were you guys running protector (the module)?
Can you look in your database and see if the data and structure is still there? (use phpmyadmin or your control panel)
I can offer you (paid) services to restore your site (if you have backups or most of it is intact) and add additional layers of security. There are many things that can be done to make XOOPS more secure, especially since it hasn't been updated in ages. (I consider myself a XOOPS expert, and have been using XOOPS for 3+ years. See site in sig for example)