salesprodomains on "Edit CSS page is missing. CSS Stylesheet Editor is gone blank!"

PLEASE HELP! the "Edit CSS" page and it's blank? The CSS Stylesheet Editor is completely missing! I have no access to the Stylesheet.
Any idea why this would happen? It was there yesterday.
When I go to: Appearance > Edit CSS > nothing is there except the "Publish" and "CSS Revisions" info on the left hand side. The right side usually has the area where you can enter your custom CSS in now completely BLANK! nothing is there.
Please help!