This is the product of far too much angst, that really wouldn't leave me alone until I wrote it down. I hope I didn't mess this up. Please read and review.
John wasn't okay.
And why should he be? He'd just lost his best friend. He had watched him step off a building and fall. He had been the very last person to talk to him, to hear his voice, to watch him living. He had the only copy of his suicide note, the verbal one he'd left through a phone and eyes that burned.
John was left with the task of fighting off the reporters. The story wasn't over yet, not as far as they were concerned. Oh, but it was. He kept his story simple and he only told it once. Everyone eventually left him alone. Except that still left the people John had to talk to. They deserved to know, and so John repeated the note as instructed. Once for Mrs. Hudson, once for Lestrade, once for Molly. He also told Mycroft, partially because he was Sherlock's brother and partially because he had messed up and let it happen. John told them not to believe a word of it, with a little laugh. Mrs. Hudson smiled through her tears, Lestrade frowned not meeting his eyes, and Molly bit her lip, almost smiling though. Mycroft stayed a stony wall as much as he could and John didn't hate him, mostly.
John became Sherlock's note.
He didn't know what to do next. How was he supposed to move on? He hadn't been alright before meeting Sherlock; he had been going nowhere, haunted by the past. Then they'd met and John had become more alive then he had ever been before, enthralled by the danger and the safety and the aliveness of everything. But then Sherlock had stepped off a building, falling forever and not long enough, and he was gone. And John was back to where he was before, except now he had seen how good life could get, what he could never get back, and it was so much worse than before.
He would go back to 221b, eventually. It was home, even though home was about people not places. It would be hard, because he would always expect the sound of a violin at odd hours, or constant chatter, or comfortable silence. John would expect strange experiments, body parts in the fridge, and guns shot at yellow smiley faces. He would expect a presence besides his own and the feeling of looking after someone and having them look after you in turn. These things would not be there. Sherlock would not be there.
The fact that John wasn't in 221b didn't mean that he didn't see Sherlock everywhere. He was in the shadows and the sunlight, the back alleys and main streets, he was where they had been together and the places they hadn't. Most of the time it was little things out of the corner of his eye that weren't there at all. Sometimes it was the swirl of a long coat, the flash of colour from a blue scarf, or just a tall thin person. Other times it was some memory, a thought that that was where they'd solved a case or Sherlock had made some particularly witty deduction or John had said something that surprised Sherlock. Once or twice, he had even thought it was him for a minute or more, until the Not-Sherlock disappeared into thin air.
It was maddening.
So, yeah, John wasn't okay. And even if sometimes he feels like leaving his own note, he won't, because he can't let Sherlock leave the world. Not yet.