This has been driving me nuts for days now. I know I have read this story 100 times and I know I have it on my favorites list on ff.net buuuuutttttt I can't remember a single thing about it except for this one scene.

Sam has a very high fever due to an injury and/or illness. I think Dean and Sam are staying at Bobby's. Dean is downstairs arguing with Bobby. Because of the fever, Sam is delirious and he sneaks out the door. He is wandering the highway and collapses. A cop sees Sam and goes over to help him. Sam is calling for Dean. The cop asks if he means Dean Winchester. The cop then says "you must be Sam Winchester. I am officer so and so and I'm working your case." The cop loads Sam into the car and drives him to Bobby's. Dean realizes that Sam is missing and is frantically trying to find him. The cop pulls up and tells Dean "I think it's past time you take Sam to the hospital". Dean agrees and I think Sam has a seizure at that point.

That is all I remember and I know I'm going to slap myself in the head once someone tells me what story it is.