Currently Being ModeratedFeb 19, 2013 10:08 AM (in response to Doelago)
Try this (from an Apple Support page http://support.apple.com/kb/HT5369):
"How can I detect displays? If the detect displays option is not available, hold down the Option key while you are in the Display pane."
It's inexplicable to me why Apple would hide the "detect displays" button. Apparently the "plug it in and it just works" concept died with Mr. Jobs.