I saw Star Wars in the theater seven times during 1977 and know for a fact that I saw the scene of Luke and Biggs on Tatooine on the big screen during the first showing that I ever saw. I also clearly remember noting that the scene was not in any subsequent screenings that I saw that year.
Folks online have noted that there must have been a cut of the film showing Luke and Biggs on Tatooine because the scene is referenced in the Marvel comic book and The Star Wars Storybook, merchandising items that would have been produced prior to the film's release. The people who produced those items must have been working with, or referencing, that particular cut. (Others, however, have suggested that one's "memory" of the scene on film is simply a product of reading the Marvel comic book or The Star Wars Storybook. That may sound plausible, but it's not in my case.)
When I first saw the movie, my parents and I were among the last people to get into the theater. As such, we ended up sitting in the first or second row. My memory of seeing Luke and Biggs on opposite sides of that giant screen is thus very distinct, and very, very different from seeing that scene in the Marvel comic book or the Storybook.
So: we can conclude that, given the scene's presence in the comic book and the Storybook, there was almost certainly a cut that the producers of those books were working to that included the Tatooine scene (and, of course, the Storybook actually includes images from the scene, which strongly implies that there was at some point an intent to release the film with the scene included). If the cut exists (or existed), it's possible that it made its way into some theaters along with the "original" cut. (Stuff happens.)
Anyway, I wouldn't just say "it's possible". I'd say that that's exactly what happened -- because I saw the scene myself.
Thus my question: Were you one of the people who also saw the scene in the theater in 1977? If so, please provide details about your experience.