When you change your username with the new mojang feature from today all items in the bauble slots are gone.
Reason: The items are save in .baub and you need to you the uuid.

If it's saved to the uuid they won't work in offline mode, you can't win this.

No way?

Perhaps Baubles should move over to IExtendedEntityProperties on the player entity instead of saving to its own files.

Yeah, this is an annoying issue, but a pain to solve - there is no easy win.

Moving the save to the player data itself might be a solution. I remember there being an issue with it on the thaumcraft side, but I can't recall now what the problem was exactly. I will have to re-examine it.