I finally found it!! In my TM, the rear shell light shutoff is not controlled by the bathroom wall, but the
bed platform. I had the
bed pushed all the way into the TM (as when you're going to break down) and I shined a flashlight under the
bed platform and viola! There was the silver button on top of the structure underneath the
bed. When the
bed is pulled out, there's a little white box looking thing (I couldn't get a picture of) on the underside of the
bed near the front that will depress the silver button down. Mystery finally solved. Now, no clue how I could ever reach either part of this mechanism should I need to be able to do so. Looks like I'd have to take the
bed apart.