Group chat suddenly missing from ALL users' iphones

Sealiney wrote:

My family has had a group chat for ages that is very active. Suddenly, in the last few weeks, that group thread disappeared from ALL of our iPhones... It's not in the deleted folder, nobody has had access to all of our phones to remove the group, nobody has been messing with their settings... What in the world?! How do we get it back?

It can be restored from backups.