You can probably abandon any hope of it ever coming back considering this :
Slayerduck on
hypnohub.net/index.php?pa...05887&pid=150#1205038 :
Fav search: the reason is that our searching is done trough a separate search database called SOLR. The favorites subset of data is not currently being stored there so it can't do the searching that way. Before the hub searched just on a SQL database and was able to make complicate (but heavy on CPU) searches like that.
also note that "fav searching" is not even mentionned in the "Planned migration/features:" of the "Site migration status / bugs" stick'd topic, which is probably the final nail in the "fav search on the hub" coffin since it show it's not even planned.
As for figuring a way to navigate favorite, my workaround to the problem is to DL them from the hub and UL them to my own personal myimouto booru with a copy pasta of their tag so i can search them around as much as i want.