3. The Ear-Piece
Telling fans "There's something you haven't noticed" is only going to lead to one thing, Mr Moffat. We're just going to analyse closer, and closer, and closer. And it was only recently that this "clue" started doing the rounds on Tumblr. There's an earpiece in John's ear whilst he's on the phone, and when he's knocked over... it's gone. Have a look above, and notice that lighter grey item on the ground, as Watson's head turns away. Is it a mistake or a red herring? Surely, John Watson can't be in on this. Can he? What if it was Lestrade that asked him to wear it, or Mycroft even? Was the cyclist employed
specifically to knock it out? Or was the ear-piece planted by Sherlock? Out of all of those, the most likely answers are probably a) mistake/red herring, or b) Mycroft. It's well-established that Mycroft relies on John when he's worried about Sherlock; did he want to report to John whilst he was watching it, and have John describe what was going on to him? We might never know: it's such a tiny "clue", it might just mean nothing.