A CNF writer could recreate scenes by asking a person who was there. Another way would be to actually go to the place and look at where it happened. This would allow the writer to understand where the scene was see and allow to include few extra details. A third way would be set up video cameras (Schrodinger’s cat reference) and review the footage. There’s a fourth which would be a speculation angle, taking the angle of what the people MIGHT have said at a certain time and place, and attempting to use the same style of speaking that the characters do.