Factual error: In the famous tugboat scene, Fannie rides out on a New York Central tugboat painted jade green - a color which wasn't instituted on the boats until the early 1960s. To be accurate, the tugboat would have to have been painted red with a black stack and the New York Central logo.
Factual error: Barbara's hairstyle is that of late 60's, when the movie was made, and not correct for the early 1900s setting of the film.
Answer: If you mean their first meeting, most likely it was a deliberate decision by the filmmakers that Nick wasn't seen in the audience. The scene was constructed to introduce Nick and show Fanny's reaction as she opens the dressing room door, seeing him for the first time. Nick being seen earlier would also have lessened the audience's reaction as well.
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