So, what, are we supposed to believe that the viewed simply vanished? Turned to smoke? Exploded into multi-colored glitter? This is a trope that is WAY over-used, and it drives me ape. It has plenty of variations, but they all boil down to the camera showing you a character's reactions without allowing you to see what they see. Sure, this can be used for dramatic build-up; for example, man sees monster coming at him (but camera does not show monster), next shot is him trying to explain what he saw to companions, allowing the watcher to relate to the companions. But when we are allowed to see the target of the view, then the target is removed, we have nothing to relate to: we cannot relate to the character, as he sees what we don't...but we've seen what he sees, so we're only fed half the info, without the use of build-up.
It's cheesy as Hell, and needs to be stopped, much like the "scary noise, person gets paranoid, opens door/cabinet/box, cat jumps out" trope. It's completely overdone.
We now return you to your regularly scheduled pablum.