Speedo Gear 1G B6

[Oldschooler]

I pulled out of a parking lot today and looked down to check my speed and it was sitting on zero. I pulled over and checked the speedo cable. I have a 1G B6 so the speedo is driven off the front wheel. I checked that and the whole drive gear had backed out of the front wheel. First I thought the speedo cable had come off but it was still screwed into the drive gear. It has just hanging there. I was able to get it back in using the factory tool kit. (gotta love it). But I didn't see anything in the way of a retainer ring or anything to keep it in. I rode about 30 miles home and it remained all the way in like nothing had ever happened. Is there something I should be looking for that holds the drive gear ( gear speedo cable screws to) in?
 

[ribbitism]

the 1st gen 600 drive gear is turned by 4 white (laid out in a + shape) tabs which slot into notches in the wheel hub. It is held in place by being wedged between wheel and fork. From the fact you've said it was found to be 'backed out' of the wheel, I think that would suggest something has failed with the drive gear itself and I would take the front wheel off so you can assess more closely what has.

I would guess something like a failed drive gear unit seal which lead to screwed up bearings allowing movement etc, or possibly the notches are worn and on their way out.
Either way, whip it off to get a better look, but I would imagine the odds are in favour of a replacement being needed since the units are normally replaced not repaired.

Hope this is of some help