To repair some hard drives safely, Disk First Aid needs to quit all applications, including the Finder. With Disk First Aid version 8.2, occasionally icons on the Desktop would not reappear until after the computer was restarted.
Disk First Aid version 8.2.1, running on iMac, automatically restarts the computer after quitting. Future versions of Disk First Aid will not require the restart. Currently Disk First Aid version 8.2.1 ships only with iMac, however, similar behavior could be expected on a different computer running this version.