'The Lost Cut' is nothing more than the initial rough cut screened in the dailies room to see how the film is hanging together. It will typically be a mix of completed scenes, B&W dailies with just on-set audio, frames with 'insert shot XX here' and so on. These are never really kept or shown to anyone, they are just part of the standard production process. You will never see anything like this anywhere as it would have only existed briefly as a spliced together mess of a thing on 35mm, and then would have been cut back up for the next run-through etc.

The only way this would exist would be if someone stole it on the day.

On people's memories of seeing the biggs scene, seeing Luke throw twice etc. I think with all the bootleg tapes surfacing, we can write those off as memory playing tricks after all these years.

I find it hard to believe (even though I have my own memories of the "She's Beautiful" line being in there, I have to concede that it most likely a manufactured memory) if for no other reason than it would be on one of the bootleg audio recordings or video tapes, and that some of those scenes would require a different score to be cut.