WARNING: The following contains major spoilers for Black Widow, now in theaters and on Disney+ Premier Access.
After a delay of over a year, Marvel Studios' Black Widow has finally hit theaters and gives context to Natasha's (Scarlett Johansson) time following Captain America: Civil War. From the beginning of Black Widow's production up until release, rumors were circulating that Robert Downey Jr.'s Tony Stark was meant to make an appearance in the film. However, when it finally hit theaters, Iron Man was nowhere to be seen.
Many of the ideas surrounding his cameo revolved around his pivotal conversation with Natasha following her betrayal in Germany. After the fight at the airport, she lets Captain America and Bucky escape while subduing the Black Panther. As a result, Tony reminds her that she is a fugitive and that General Ross is coming for her. Black Widow could've added to this scene with Tony providing her with a head start in some capacity, but instead left the super spy to her own devices.
The rumors continued to fly that the scene would involve cut footage from Captain America: Civil War or various other camera tricks to show Stark in the scene without actually being there. Reused footage from the previous film in canon could have worked well from a narrative sense to help shift the tone of Civil War over to Black Widow. Instead, following a prologue, Black Widow opens with Nat already being hunted by Ross. But even though Tony's potential role is cut, it doesn't mean he was never in the film.
Before a film releases, it will typically go through test screening with a small audience. This is where viewers can see a rough cut of the movie without special effects and scenes that may or may not stay in. This comes well after initial cuts of the film are made, with changes being made as audiences give their feedback. For example, one of the scenes that could've been a part of this may have included Stark's cameo. This would explain how Nat got such a massive head start on Ross after immediately running off after the airport fight.
Ultimately, Black Widow excluding Stark's potential cameo became a great decision for the film as it shows that Natasha doesn't need help from the Avengers to do what she does best. However, since the rumor of Downey Jr. appearing endured for so long, it's always possible there is a scene or version featuring the hero. It's a mystery that may never get an answer, but it doesn't necessarily need one either.
Directed by Cate Shortland, Black Widow stars Scarlett Johansson as Natasha Romanoff/Black Widow, Florence Pugh as Yelena Belova, David Harbour as Alexei Shostakov/Red Guardian, O-T Fagbenle as Mason and Rachel Weisz as Melina Vostokoff. The film is now in theaters and on Disney+ Premier Access.