I am dying to find a specific fic that I've read where Sam is cursed or spelled into a spirit state and he can only communicate with Dean through dreams despite being able to wander around the bunker and watch Dean freak out. Dean doesn't believe that it's really Sam talking to him until Sam leaves a bunch of hickeys on him and finds a witch to reverse whatever spell was cast. I did also find it on AO3, but none of my searches seem to be hitting the right keywords. Any help would be much appreciated.