ahhhh! I lost some important files!

So had a problem with my external hard drive. All of a sudden got this "file unreadable/corrupted" message. I'm thinking uh-oh, tables/indexes messed up. I did a scandisk and it "fixed" the problem...but now some folders are missing!

The space is still being used on the hard drive..but not showing in windows explorer. Can anybody give me any sort of direction to begin at?