Dome & Shifter Illumination Not Working - Lots More Details Inside

#1
I have a 08 Corolla CE which dome (interior roof) light and the transmission shifter illumination (light under PRNDL) is not working.

I don't drive the car often, but apparently, the dome light went out first then the AT shifter light was out a few weeks later.

The switch to turn the dome light to on/door/off is missing. That is, the little plastic knob/slider. But this only went missing after someone else tried to diagnose it. The dome light was not lighting before the knob/slider went missing.

I have a page out of the Haynes manual concerning the "Interior Lighting System". This might help, and I've tried using it. Just a note, the problems are "A/T Shift Lever Illumination", and "Interior Light", I believe. The term "Rheostat" I think is the dimmer switch.

Here is a link to it:
https://www.dropbox.com/s/x4d33qmaojfj7gi/CES.pdf?dl=0

Here's what I've done/noticed. None have led to a diagnosis...

1. Checked all the fuses under the hood, especially the one that says "dome" (or something like that). I even switched every one of them with the spares. I also switched the relay for the dimmer switch with the one for the headlights (they were the same).

2. Checked the dome bulb by connecting it to an external power source, lights nicely.

3. The dimmer switch dims the other lights inside that can dim.

4. Everything else electronic, including outside lights and trunk light, defogger, and all other lights inside and on the dash works.

5. The battery shows normal voltage with and without the engine running. I would use a multimeter on the dome light assembly, but I don't know which position the knob/slider is in. I could not see anything the I could maybe move with a screwdriver to more the switch.

I know this is not too serious, but it is important for safety concerns. I would really appreciate any help.
 
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