How did you go about reformatting it? It sounds like you actually cleared the partition information. Your data is still there, still intact, and the master file table should still be available. However I don't know of a way to restore the partition information using the existing data, at least not for certain.
Programs like Partition Magic (there are some free ones with a little fewer features I think) might allow you to see that the partition is there. You can also search for "data recovery software" or "file recovery software". If the file table is intact, those should be able to locate and restore all of your files, since it can read the table and get the files just like the OS would. It just scans the drive until it locates a file table, if there is a good one. If the file table is gone, then it can scan the drive and attempt to restore files based on recognizable file patterns.