This was a specific fic I remember reading. I remember most of it, just not the title. In the fic the Mark of Cain eventually messes Dean up so much he loses contact with everyone, and everyone sort of lets him (as a side effect of the mark). He goes to Mexico, learns a bit of Spanish, and gets a job where he ends up cutting off his own arm "on accident" to get rid of the mark. Everyone thought it was because he was drunk (Dean is an alcoholic), and eventually Dean ends up going to AA meetings. A lot of the story revolves around him recovering from alcoholism. There's a family living next door to him that he becomes good friends with. Back in America, Sam and his girlfriend (an OC), as well as Charlie and Cas (who is a professor) all hang out once a week for movie night, and they slowly start realizing, wait, why did we lose track of Dean? And they track him down via Charlie's computer skills and Cas's mojo. Dean was going under an alias. Sam and his girlfriend send him an email and go and meet him.

I think it was on Livejournal? I just can't remember the title! Does anyone know it?