All bugs › Followers (Lydia and others)
Lydia (or another follower) vanishes when a quest gives you a temporary partner
What happens
During quests that assign you a partner who automatically replaces your follower, Lydia may vanish if you didn't manually tell her to wait first.
PS5-safe fix
UESP lists no console-free way to bring her back. Check her home first (Breezehome if you bought it, otherwise Dragonsreach). If she's truly gone, reload a save from before that quest.
Prevention
Before any quest that hands you a temporary partner, tell your follower to wait somewhere or dismiss them yourself.
Always make a hard save before trying a fix.
Tried the fix and it's still broken? Tell us so we can update this page.
Still broken on my PS5