The Gradient Annotator is an essential part of Illustrator’s Gradient tool (G). That’s why it’s such a pain when it seemingly disappears! I get emails about this all the time so I think it justifies a quick post. If you don’t see your annotator when using the Gradient tool (G) then choose View > Show Gradient Annotator (Command-Option-G/Ctrl-Alt-G). I tend to sometimes turn it off and on by accident when I’m using the keyboard shortcuts for grouping and ungrouping objects.