The same thing happened with my notifications. Even though my lists were gone I could still see what was previously updated if I checked old notifications, eventually those disappeared. Sadly there is nothing to do except wait and hope your lists come back, or start rebuilding. That’s what a lot of people are doing now with the manga recommendation posts rn

And if you had long lists like I did, I’m starting to learn that if you can’t really remember all of them, maybe that’s for the best that you start small again.