Any mistake that the conspiracy makes will look silly in hindsight, because we'll only be looking at that one detail and wondering how they could have missed that. Bear in mind that the conspiracy is faking a huge amount of information, and that they have to keep producing more and more photographs, data, and everything else that they need to go through the motions of being a real space agency. A little mistake like this wouldn't be as glaring or obvious to them as it to us.
That being said, I doubt that this is anything more than a rock.