Black screen - HD works fine

Model: a1502

Working fine then closed it came home from work and no screen. Nothing, black, no logos, nothing. Been researching but cannot find conclusive answer.

-Black screen but HD still works fine

-Pram and smc reboots do not work

-external hdmi monitor shows full OS X without issue (backed up to time machine) but does not show the laptop display in display preferences

-brightness keys do not respond

-nothing plugged in, besides hdmi for monitor

Have appt with "geniuses" tomorrow but would rather get info from this forum before.

Any ideas?