There is no way to undo what Chkdsk did and yes, data loss is always a possibility with Chkdsk which is why I like to have data backed up safely elsewhere before running it. GetDataBack is a good data recovery program and if it was unable to retrieve your files the only recourse you have now is to send the drive to a professional data recovery company. If you want to make sure you get the data back, don't use any other data recovery programs on that drive. If you absolutely know you won't spend the money on professional data recovery and your insurance won't cover the loss (see below), then tryR-Studio as a last resort.
I use DriveSavers for my clients who need professional data recovery. General prices run from $700-$2,400. I understand that some insurance companies are now covering data recovery costs so check with your insurer. Homeowner's/renter's insurance policies will have the coverage under "Loss of Intellectual Property"; business insurance policies will have the coverage under "Business Interruption".
Drive Savers - http://www.drivesaversdatarecovery.com/
MS-MVP - Elephant Boy Computers - Don't Panic!