Here is the fight between Bellator fighters Chad George and Mark Vorgeas. From the outside, it looks like just two men just trying to jock for position and submit each other but we were wrong, even the referee didn't see that Mark Vorgeas was already unconscious and completely out.
MMA Fighter Chad George executed the Von Flue choke with around a minute and a half remaining in the first round. You will notice the fighter's bottom hands slowly loses its grip and the fighter on top had to point out that his opponent is out.
The referee clearly failed to see the situation in this instance.