I'm looking for a specific story--and the sad thing is I know I have it saved, I just haven't tagged it right. It starts out with Sam being hurt from a previous case--I'm not sure if we ever find out exactly how/why he was hurt. There is a dog who has "adopted" Sam but he's hurt enough that he can't even lift the dog. The owner of the motel they are staying at has a granddaughter who loves the dog (and possibly they leave the dog there with them when they leave). They are working on a case, against a wizard (I think). The wizard has a piece of material with different magical symbols/markings (?) on it and somehow one of the boys becomes affected by it (maybe Dean) and they have to get the material back to save...one of them. Sorry, I'm just trying to put out all I remember from the story!
I know it was gen, and am 95% positive I read it on FF.net. It might possibly be part of a series. Thanks so much for searching--everyone here is awesome!!

ETA--the story has been found and the link is in the comments :-)