I'm trying to locate a story I read ages ago and promptly lost. It comes back to me every now and again when I'm skimming through other works, and I always think, "Damn, I never did find that story, did I?" So now -- trying to make things right and give a good author his or her due.
All I can clearly recall about this story is that Dean and Sam were chilling at a motel somewhere, Dean went to get food, and suddenly he jumped forward about a week or so in time. I don't think he realized anything had happened (except, perhaps, the sun had moved in the sky?) and slowly comes upon the horrible realization that something awful has happened, and particularly, that he's been forcibly pulled from Sam for at least a week and his brother has no idea where he is.
I believe this took place within the timeline of the show (i.e., they are both adults), and I don't think it was slash, but who knows.
I hope this is enough for this awesome community to go on. Thanks!
EDIT: Found! This community rocks! The story is
Short Trip Down a Long Road by K Hanna Korossy, and huge thanks to
de_nugis for the crack detective skills.