Well, if you had installed iTunes (dreadful as it can be) it would have backed up your phone, and you'd be able to restore it. Unless, of course, you've Jailbroken it, in which case you deserve what you get
A key philosophy behind Apple mobile devices is that users don't have to worry, care, or think about filesystems. This is exactly why! Anyhoo...
Is your best bet not just to copy what you can from it, do a factory reset, and start over?