I have never tried recovering deleted files from a SD card but reading of your predicament I checked the software I have which is designed to retrieve files that for one reason or another have been deleted from a hard drive.
The software did detect my SD card when I connected my camera to it.
What you could try is download the trial of the program which will scan your SD card to see if anything can be recovered. This will at least let you know if there are any files there.
The trial version will not undelete them, you would have to purchase the product. Having said that, as mentioned by HeinzOz you could then do a Google search and find plenty of alternatives and so you can then compare prices etc.
Link to the trial software.