FWIW I’ve just solved mine too, at least I think I have. I was looking through other forums and suggestions and one of the common things that came up was to try disabling plugins. I disabled everything I had and reactivated them one by one.
It appears that my problem was something to do with a contact form named WP-Lightform. If I enable it, my visual editor disappears. If I disable it again, it’s back to normal.
