You do not have to see anything on the screen.You can follow the path to the Picture mode. Just check the User Manual of the TV set. Pick up the remote control unit and pretend browsing through the menus. Take a couple of seconds between button presses because it may take some time before the menu changes on the all-black screen.
Sometimes my computer's monitor goes blank due to whatever reason it may be. I know the path to restart option in Windows. So I start with the Windows button on the keyboard and using the arrow keys ( left-right-up-down ) I navigate to the restart option and press enter.
Anyway, as I told you, this was a remote possibility because resetting the TV should have returned everything to the factory mode. But wait. How did you do the resetting ? Isn't it a menu thing, either, which you can't see ? Is there a physical reset button on the TV case ?