2
Your database was simply deleted? Sounds like
a) Host hacked
b) Host messing up
c) Exploit in your XOOPS with a database administrator account
If it is not the 2 first ones, I can only recommend that you in the future get a database account without database creation/deletion rights. XOOPS needs to be able to create, alter and remove tables, but the database user should not be permitted to create or remove databases.
XOOPS is quite secure, but there can never be 100% security - especially not with custom modules, which may open up for security risks.