The problem was the disappointment at the line being missing, I can understand remembering a visual differently, or a garbled version of a line being in my memory, but two actual lines of dialogue, which it now turns out are in the novel I think strengthens the case that it was in a print at some point and was trimmed out later.
I'm trying to think of a way those lines could have been planted in my brain between the first 22 times I saw Star Wars and then next 17 times I saw it 6 months later (My dad was the projectionist at the local cinema at the time). I can't think of a logical way I could have received those lines into my head in between those two times. I admit it is possible, but I can't think of how it would have happened, other than if it was in a trailer or an ad.
When did the novel come out BTW?