The selection must have been saved using the Save selection Action; if this is the case, you will find it in the Restore selection from list.
If the selection is no longer available (for example because it has been removed from the Action List), you will get a warning: "Restoring unknown selection".
Select by color space <! -- Select by color space Select CMYK --> Save selection <!-- Type "As CMYK objects" --> Convert to RGB objects <!-- Convert color --> Select all <!-- Select all --> Apply RGB curve Select by color space Restore selection <!-- From the list, select "CMYK objects" -->