As always: *SPOILER ALERT*
I have noticed significant buzz on the internet over the gun Moriarty used to shoot himself. Apparently, the gun is not in his hands as he falls down. After reviewing the clip, it appears that they are correct. It appears his very blurry hand is not holding a gun.
One video calls this “the clue everyone missed.” This is a bad title because A.) a lot of people noticed it, and B.) it is not a clue. This is nothing more than a continuity error.
If the gun did disappear, Moriarty would have had to have put the gun in his mouth, pull the trigger, hide the gun, fall down, and get the gun back in his hand. I find it hard to believe that he could have done all of this without Sherlock noticing.
A disappearing gun is not how he survived. If you are looking for how Moriarty survived, this disappearing gun theory is not it. Look elsewhere.