MacBook Pro: External display works, LCD display not recognized
Yesterday I restarted my Macbook Pro to find that the LCD display wasn't working -- there's not even a dim picture, it's just completely black, as if the display was asleep. Up until that point, it had been functioning completely normally, no visual glitches or issues -- the display simply didn't turn back on after restart.
When hooked up to an external display, the computer is still fully functioning. I can tell by looking at the computer's "Display" list that the LCD screen isn't recognized at all -- the only display listed is the external one. Furthermore, when I press F1 and F2, as you would to adjust the LCD brightness, no onscreen graphic appears. And finally, when I close my laptop, the computer doesn't go to sleep like it usually would -- it remains functioning with the external display.
All of which is to say, as far as my computer knows, the LCD display is completely nonexistent.
Does this seem like a problem with the display cable, the LCD screen itself, or some other element?