I don't see any reason to answer in Thorsten's forum because the thread started here.
Restoring of the database took in fact place without problem. Anyone can find detailed information and support at the phpBB forums themself.
If the ISP can be forced to deliver any backups depends on the contract and the local laws where the ISP is located IMO.
Of course it is better to have more than one backup in case one is broken, crackers have placed something in the database what works with some delay, etc, etc.
Volker