Might want to watch this segment from Lou Dobbs show last night during the rally.
Joe DiGenova and Victoria Toesing made a few key points.
The last one at the end - near 8min is the interesting one.
https://video.foxbusiness.com/v/6060523446001/
Youtube not displaying the show from last night otherwise I would embed.
JoeD states that Mueller took his phone into the Oval Office and it is believed that he live streamed the meeting with Trump back to FBI HQ. And left it there to catch the 'after conversation'.
Victoria postulates that they can't get in there with cell phones now, so how could he have taken a phone in?