Hello there. I seem to enjoy ripping my heart to shreds as much as Moffat does, so I wrote this sad little ficlet. It's 221(B) words, but this author's note makes it longer.
John might be just a little bit insane here.
After Sherlock dies, John can't help but see the detective in heads of dark curls, long coats, pairs of bright eyes. And when that hair, that coat, and those eyes belong to just one more ordinary stranger walking London's streets, John takes a deep breath and clenches his fists.
He gets another job: an ordinary job, working as a doctor, not solving crimes. Lestrade doesn't call, and neither does Mycroft. John still lives in 221B. Mrs. Hudson talks to him sometimes; makes him food, straightens up after him. For the most part, John is alone.
He tells himself he doesn't mind.
Dark curls, black coat, bright eyes. They follow him everywhere he goes. At first he thinks it will drive him mad, but things get better with time. Every time, he tells himself: they are not Sherlock. Sherlock is dead. He is not coming back.
He is never coming back.
So when the day comes and a man with a dark curls, a black coat, and bright eyes shows up at John's doorstep and says "I'm back, John," John shakes his head slowly and gives the man a sad smile. It wasn't his first hallucination or the first time Sherlock came back to him.
"No," John says, "He's dead. He's never coming back."
And he closes the door on the stranger.