I'm not the expert on this since I have never done it. It sounds like you may need a data rescue program like Data Rescue III. I believe you can download a demo and see if you can see the files. If you can, then you can buy the program and retrieve the files. I don't know if Disk Utility can restore them--I think they have to be visible but this is not something I have ever had to do.
In the meantime, don't do anything with the drive--you don't want to overwrite any files. Hopefully all or most of the files are still there and you will be able to retrieve them. The less the drive is used, the better your chances are of retrieving the data.
Forgive me for not realizing that there were files on the drive that you wanted to save. Upon re-reading your question, I now see that there were. I should have known to warn you, and my bad that I didn't.
Good luck!