Pet disappearing bug

This bug occurred while I was defeating an ender dragon in adventure mode. I was moving over a glacier and the cat disappeared without a death log. I backed up, changed the mode to creative and looked for it in commands but could not find it. You can see it at around 6:25 minutes in the link, so that will give you an idea of what happened.https://youtu.be/0CXa5UEIcCk