I have a level 102 pet - Is there a chance of getting "back to level 1"?  I *thought* that didn't exist past level 5+ ish.  But I read recently on Jellyneo that it is possible.  Does anyone have any evidence?

Personally, this never happened to me BUT, i did notice a neopets' stats on TDN that had  VERY high stats in everything (except defense for some reason) and their level was still at one. 

It certainly happens after level 5+ but I'm not sure if it could happen at level 100+

I've also read in the past that it could happen but that it would be rare. Jellyneo says the following as well:

The outcome "Back to Level 1" becomes a very low possibility if your pet's level is high, which is estimated to be at around level 20+ or 40+. In some rarer cases, your pet can still go down to level 1 from much higher than this, with no confirmed cut off that it is guaranteed to no longer be possible.

I've never really logged my zaps, so I don't have any proof of it happening.

The jelly neo article was what I read that made me question it.  I've mostly been zapping my secondary pet for months now because I didn't want to lose my species specific healer

As Erebos said, I too have stopped zapping my battle pet because I don't want to lose my species specific freezer.  I have a bunch of Lenny MPs in my SDB just for that reason however, and in case of any other adventitious events.  It was always my understanding that, although quite rare, you could get that unlucky zap, bringing your pet back to level 1, at any time.