Well first, I'd be sure the drive was finalized. Load up some burning software on your computer and see if the disk can be closed/finalized.
If you search around, you can find unformat guides and programs, as well as undelete software. However, I've never had too much luck with them... Someone suggested this one program to me. I can't recall it's name right off, but I was told it's pretty good. PM me sometime if you want the name. Oh, but I'm quite sure it's not free...