Recovering an accidentally deleted  folder in OSX - no Time Machine or backup available
Data Rescue is a long time favorite for undeleting files. It is not free, but you can download a free trial to see if the folder and files can be recreated before deciding to pay for the software or seeking professional recovery.

Similar to Windows, OS X doesn't wipe the files but instead marks the directory entries as free. As long as the files do not get overwritten (say you powered off the Mac immediately after the error was performed) you should get most of the files back. It all depends on chance that the system didn't overwrite the files as part of the normal shutdown process.