It's a dark and terrifying story and for some reason it's haunting me so I'm hoping if I find it and read it again (and if the ending is even a bit happy--I can't remember) I can put it to rest.
Out of desperation Dean ends up agreeing to do something sexual with this awful man who lures him into a van and then tries to rape him. Dean fights him off with a small knife but I think he drops the motel key running away so he has to get back to the hotel and figure out how to get Sam out before this man gets there.
Thanks if anyone finds this story!
Edit: I remember a couple more things about the story: I think to escape the Bad guy who has the motel room key, Dean and a very sick Sam go out the back window and they hide out in the woods? And at some point, not sure how, Dean finally calls Pastor Jim, I think? Also, there's a woman with the bad guy (she's evil too) and Dean gets away from the man and woman by using this little knife--it might be something like a swiss army knife corkscrew which he stabs the guy in the foot or leg with?