At Second Sight

“John”, he breathed in a deep voice. “You’re awake. You’re finally awake. I …” Eyes of an undefinable colour observed him with obvious concern. “I’m … I …” The man coughed uncomfortably. “I should get the doctor.” With that, he stood up abruptly and hurried out of the room. It looked like he was running away.
John stared after him. He was so perplexed that he almost forgot about the throbbing of his head. What had just happened? Why was the most gorgeous man he had ever laid his eyes upon keeping watch at his side?

After receiving a heavy blow to the head, John doesn't remember his relationship with Sherlock. That doesn't stop him from immediately falling in love, though.