I don’t think he forgot about that scene, I just think he kinda sorta wrote himself into a corner. Padme would have to die somewhere in the prequel trilogy regardless. It is bad story telling to have a principle character survive a chapter, but to never be shown again in the rest of the story.
But her disappearance was already explained in the 6th film, so there was NO need to kill her off. That’s not bad storytelling. What is bad storytelling is to contradict so many things in a saga where the second part was filmed prior to the first part, where the story was already set, but you still end up screwing things up that were mentioned in the original films. For eg:
OT- Owen was afraid that Luke would follow Obi-wan on some damn fool idealistic crusade, like his father did
PT - Owen never even met Obi_wan while anakin was alive and Anakin didn’t follow him on a crusade either as, by the time owen was even in the picture, Anakin was already a jedi and it was Qui-Gon that he followed originally
One of many
Here’s my final post on the matter.
“The part that I had never really developed is the death of Luke and Leia’s mother. I had a back story for her in earlier drafts, but it basically didn’t survive. When I got to JEDI, I wanted one of the kids to have some kind of memory of her because she will be a key figure in the new episodes I’m writing.”
–George Lucas, Star Wars-The Return Of The Jedi: Annotated Screenplay, 1997
“Leia’s recollection as described in Return of the Jedi have no inherent flaws and are valid given the greater context of the saga. But I suspect those looking for contradictions always find them.”
–Rick McCallum
Rule #1 = George revises his own history as he goes along. But the fact that its even explained in the novel and was part of the original script ( including Owen being Obi-Wan’s brother) proves that she was supposed to have lived and that her surviving ROTS made more sense with what is spoken later on in the saga.
Rule#2 = Rick McCallum excuses are common during his “suck up to Lucas years”. Not so much nowadays