This one's set during the first Tuesday in "Mystery Spot", in case it's not clear. Not really a missing scene, just an interpretation I guess, inspired by Jensen's amazing eyes.
Time seems to stop as Dean goes down. It's not until Sam's holding him in his arms that it jump-starts again.
Dean clutches Sam's shirt, struggling for breath, large, pain-filled eyes stare at him, speaking words he's unable to voice.
Don't be afraid, Sammy. Sorry Sammy. Oh god, it hurts Sammy. I was dying anyway Sammy, better than Hellhounds though, right?
As the light leaves Dean's eyes, Sam wishes for another chance to save him. He sobs and suddenly he's back in the motel room.
"It's the heat of the moment…"
"Rise and shine Sammy!"
Just a dream, thank God…
There you have it. I hope you enjoyed! Please let me know what you think!