Sherlock didn't know about the true way to treat a concussion, that's why he kept John around, his expertise were not medical by any means. He found the human body, when it was alive, to not be at all interesting. He was not trained, and the not sleeping was simply something he picked up via osmosis along the way and had never bothered to check.

The answer to that question was a resounding yes. He had missed Moriarty deeply, they were two sides of the same coin and it was so much fun flipping that coin to see where it would land. He had been bored out of his mind, nearly literally, with his thoughts flying all over the place and unable to be tamed, but now he was sharp and focused and interested.

"No."

That, of course, was the correct response.

"You're a spider, I don't miss spiders, I squash them under my heel."