Favorites, collections or settings disappeared
Before assuming they are gone, check the four places they usually are.
Favorites and layout belong to a playlist and a profile. Most disappearances are really one of those two having changed.
1. You are on a different playlist
Favorites follow the playlist they were made on, because channel identities differ between services. Settings, then Playlists, shows which one is active.
2. You are in a profile
Kids and Private keep their own favorites and layout. Long-press the Live TV tab to leave Kids, or go Home to leave Private.
3. The playlist was re-added instead of edited
Deleting a playlist takes its favorites, pins and hidden items with it. Re-adding the same playlist creates a new one with a clean slate. Editing keeps everything, which is why Edit Playlist exists.
4. Something is hidden rather than missing
Control Center, under Settings, lists everything hidden, locked, pinned or reordered across the app, with a reset for the lot.
Getting them back. If you exported a backup, import it and choose only the sections you want. If your devices share an account and your plan includes cloud sync, another device may still hold the state.
Related reading: why favorites vanish and how to stop it.