Still no conclusion as to what happened, but the current theory is perhaps as her big teeth were growing in, the baby tooth had not fallen out yet. That can kill the root but of course I wouldn't have been aware of a problem. If this is what happened the root was dead or dying and perhaps the tooth was getting looser and looser over time with all the chewing and tugging.
This theory is supported through the fact that her grip has improved. For a while she was being very chompy and having a weak grip. K agreed at training on Thursday her grip was much stronger. Wonder if this means she'll be able to hold onto a long bite now. Now that the tooth is out, if it was loose it was probably causing some pain which is now gone, allowing her to bite better.
I know as a baby I had her put under an a lower tooth near her lower canine pulled because it wouldn't come out. I think I waited too long because the tooth that came in under it is all nasty and brown. So if it happened to one of her teeth, guess it could have happened to the other as well.
Still, it sure was surprising to open her mouth and find a canine gone.