There as yet to be a third flight. DARPA is surprisingly open about the Falcon HTV-2 test flights. The releases have included more info that I would have expected.
DARPA was actually live tweeting the 2nd flight.
DARPA was actually live tweeting the 2nd flight.
As "open" as DARPA is they are subject to confidentiality and are only allowed to disclose what the DoD allows them to disclose. I am no conspiracy theorist but compare the shape/light of the aircraft in my video to the artist night time rendition from the OP article. Even if the aircraft in my video is different, I can tell you I have never seen anything anywhere near as fast as the aircraft in my video including F-15's, F-16's, F-18's or the space shuttle when it lands (which breaks the sound barrier at very low altitude).
There is a Air Force Base very near (10-15 miles)in Homestead, FL and a Navy Base in the Keys (over 100 miles), still it not unknown for the Navy to do exercises that far North, but I think a single aircraft at night might be unusual.