Something similar happened to me on my 65. Trying to pull the plug off the switch, the entire plastic back of the switch pulled out of the die cast body. I had another switch, so I just used that.

But it should be no issue to put it back together. Loosen the small Allen head grub screw in the knob. Remove the knob with the center washer button from the main shaft. Unscrew the small retainer ring, remove the trim ring and the body will come out of the dash from the back.

Reassemble it as seen here. Notes: the main shaft has one large, one small leg that fits through the switch disc, it can only go one way. The red dot; shows the position of the button on the disk lining up with the detent on the switch back. When stacked correctly, press the back into the body (you may have to bend the tabs out just slightly before), then slightly ease the body tabs back when in with pliers against the plastic back. The little lockwasher fits over the threaded portion of the main body. The grub screw locks into the groove on the mainshaft when finishing up.

I never put mine back together, but it seems doable.

Thanks for the pictures and help Mark! Much appreciated!!
Going to see if I can figure it out on the weekend.

I have the pin and spring. Who knows where all the other parts landed though...