the trick to this video was revealed on some website years ago. there is a cut at the 6 second mark. But that's not just it. when the girl goes back, you can see a little of her shoulder,  she actually drops to the ground and crawls quickly goes around the corner. Supposedly it was done in one shot and in the unedited video, which no one has ever seen but a few, the girl was slightly caught dropping to the ground. because of this they had to edit it. the edit removed that part and allows it to seem like she's suddenly not there. but in reality she dropped and crawled under the camera's view. after the cut, the camera is still looking forward because whoever shot it was making sure the girl was crouched down and going around the corner. that's why we don't see him going back. you also don't get a full shot of the corner until the girl is fully on the other side. the camera stays focused on the wall a few feet above the ground to give enough time for the girl to take off.