Database reverted to default after hard drive failure

So, here’s my story:

1. I putzed along, blogging as usual.
2. My host’s hard drive crashed. They replaced the drive and restored everything from their most recent daily backup.
3. I go in to see how things are doing, and all my files have been restored to perfect health, but my WordPress database has not. It’s been replaced by a blank WP database – with the “Hello World” post, just one category, etc. – and if I visit the admin pages I’m invited to run install.php.
4. Tech support is turning out to be less than stellar. They’ve told me that they restored everything from backup, and it should be fine, and I should be keeping regular backups anyway. As it happens, my last backup is from the end of February, so I haven’t lost everything… but still.

Does anyone have a clue about what might’ve happened? Or clever wget scripts to pull everything out of Google’s cache? I’m suddenly afraid that the same backup problem that afflicted my host, has affected my own backups as well – I haven’t ever needed to restore from them before, so am not sure if it’ll actually work or not.