That camera, even looking at the ‘raw’ footage, captures 1 frame/second, typical for a security camera that is more so for seeing who is at the gate. You’re going to get nothing of actual use out of that footage, whether the :20 frame is there or not (and that might be nothing but a white frame from the flash of the explosion).
And you must remember that the Pentagon was in the midst of an upgrade to the entire structure to strengthen it against attacks (how ironic) and other disasters. The section that was hit was already completed and considerably stronger (thicker walls, more reinforcement, heavier windows, etc). Now, a plane made of light wieght materials travelling over 350+mph hitting a heavily reinforced wall… not much is going to survive. I have seen pictures of one of the turbines sitting in the building (I think it made it to at least the third or fourth ring).
Conspiracy theorists are no more than people with too much time on their hands. Find something better to do with your time.