Smart to remember too that we're only seen half of a second of Libby's video. RA doesn't know how much was captured. He knows what happened, but doesn't know when the video stopped and started.
And neither do we.
At a minimum, there's the encounter. There's the command. There's perhaps the appearance of a weapon and a racking. Further capture of either girl, her voice, and struggle, case closed. They got their man.
The only person with a motive to deny seeing them is The Last Person To See Them.
JMO