You can try rebuilding the icon cache
http://www.sevenforums.com/tutorials/49819-icon-cache-rebuild.html
You can probably correct this with the System File Checker
http://www.sevenforums.com/tutorials/1538-sfc-scannow-command-system-file-checker.html
But it will remove the 3rd party theme and changes. You would have to repatch your system and reapply any customizations.
A Guy
Do you still have the theme activated?
Have tried uninstalling that theme to see if the icon appears again, theme packs normally come with an uninstall file.
Regards,
JDobbsy1987
hmm is it rebuilding the icon cache that will remove the customizations or the system file checker?