Instead of up and down, it is right and left...but nevertheless, the switch stays in the middle.
Like blackMB-d JS
said, change the fuse and try the rear defroster again. If you still see no control light, you should check possible power on the rear screen with a test lamp...
You can take out the switch side by side with a little flat screwdriver that is stuck under the switches side. You can check whether you have power at the back of the switch (and whether the connector is still plugged on).
The dash illumination in the switch is supplied by a coaxial cable, so the (possible) presence of dash illumination in the switch means nothing regarding to the rear defroster.