The Slimer/Libby shot *is* described in the November '88 and the February '89 versions of the script by Aykroyd and Ramis.
But that in itself is part of why I don't think it was ever in the movie.
I've told this tale many times, but... I was penpals with James Van Hise while he was writing the NOW Comics Real Ghostbusters title. I'd sent a fan letter to the comic mentioning that I had every episode of the cartoon taped on VHS, and funnily enough he had no way to get copies of specific episodes from Columbia, so he reached out to me and I provided dubs.
He told me he was adapting the sequel for the comic, and since he'd previously sent me some really great items as 'payment' for the tapes (like a copy of Making Ghostbusters, the UK novelisation of GB1 by Larry Milne, and a photocopy of the GB1 script), I naturally begged him for a copy of the GB2 script.
He said he couldn't send me one til the movie was out due to his NDA, but he wound up cutting it VERY close. I went to see the movie twice on opening day June 16, 1989 at the noon and 2pm matinees, and when I got home there was a copy of the GB2 script in my mailbox.
Which means from day one, I saw the film, saw it a second time, and then read the entire script.
And I have absolutely ZERO memory of seeing Slimer fly out of the crown of the Statue of Liberty, even though it's described in that script.
Seems like if I'd just seen that image, twice, and then read it in the script within a six-hour period, it would definitely have been "locked in" to my brain.
[I also kept a small notepad in my hand and jotted down first impressions of the film IN THE THEATRE. I will double-check, but I looked at it last year and saw no mention of Slimer at the end.]
Now, to be totally forthcoming, I have long believed that the film I saw on the big screen had minor differences to what came out on home video. The gut feeling was that during the "We're Back" montage and the end credit montage, certain things were swapped around and/or deleted.
But never once did I think, "Hey, what happened to Slimer at the end?"
So even if definitive proof of a Slimer/Liberty shot somehow were to surface, I would still be the cognitive dissonance guy saying, "Well, okay maybe the rumors were PARTIALLY true, but there must have been different theatrical prints, because he wasn't in the one that *I* saw..."