They can later just cut back to that scene, and slowly pull back and reveal that it was watched by another being who at the time unknown to all was a viewer stand in, but now has significance too the story. They did stuff like that before. Once they recorded the first doctor talking to the screen in an abstract environment about nothing in particular. Much later writers built a story involving all the doctors up to that point and stitched it around these clips. Something similar can still be done here