The thing is, there is plenty from 1977 for us to pour over and nothing indicates any other cut of the film. Check out this thread for a list of original 1977 audio recordings made in theaters - http://originaltrilogy.com/topic/Theater-Performance-Preservations/id/12161
Whether the Jabba scene was filmed with the intention to cover the actor with stop motion animation is a valid question. However, the scene was filmed and not used. It is in the novel, the comics, the special edition, and pieces of it have a appeared over the years. It is more likely that you saw a clip and your memory has inserted it into the film.
The audio for the 1977 release is well documented. The 6 track version that went with the 70 mm is the same audio mix as the matrixed stereo version (save for the low frequency channel). The mono mix was the only new one and even it isn’t all that different from the stereo version. We have some very early recordings, in particular of the 70 mm - a type of print that was way too expensive to make to make changes to. Once the film went into distribution, Lucas lost all ability to control it. It was, after all (and still is), the property of 20th Century Fox. He was given a chance to tweak the end credits and make a mono mix of the audio for the film to be better compatible with theaters that hadn’t updated yet, but this was to 20th Century Fox’s advantage because having a mono soundtrack increased the number of theaters they could sell it to. But there is not one shred of credible evidence that there was ever anything but those two cuts of the film. And the 70 mm version is archived in the 16 mm copy (with the very slightly different end credits).
This is quite different from the well documented rough cut of Blade Runner (now available) or the 70 mm cut of TESB where we have tangible evidence that there were noticeable differences in the cut. Many movies have rough cuts or test screenings, but the only other version of Star Wars known is the B&W rough cut that caused Lucas to fire his first editor. The cantina sequence from that cut has been released twice as a bonus feature (the Behind the Magic CDROM and the blu-ray box set).