imagine that after the battle, with thorin, fili, and kili dead, bilbo holds the acorn, the arkenstone, and the ring in his hands and wishes that he were with them. and because these are all powerful objects in their own ways, they grant his wish and the spirits of thorin and the princes are now tied to bilbo but because the ring is an evil douche and the arkenstone is only there to ruin everything they make it so that bilbo can't see, hear, or communicate with the durins right away. so thorin and his nephews spend for-freaking-ever trying to figure out how to communicate with their burglar.
but by the time they figure it out (because only they could instigate it), bilbo's already half crazy because of the ring and thinks they're only visions of the past or something. and bilbo's only just starting to believe that they're there and he can see and talk to them when frodo has to go destroy the ring and because the ring was the main source of the power for the curse thing, the durin's spirits are finally transported to mahal's halls.
and bilbo is bereft because he can't figure out what he did wrong again
