The sandstorm sequence never was "lost". It like all the other deleted scenes are rotting like the negatives of the original star wars trilogy in the Lucasfilm archive. Even with the cold storage vault method, a lot of these scenes need repair and cleaning color correcting to allow them on a dvd release.
The proof the scene was never lost the half a second clip in the revenge of the jedi teaser.
Also evidence exists in the making of return of the jedi from ballantine. The shot the scene and nothing was wrong with it, they excised it for pacing reasons. According to the producer howard kazanjian.
If it really was dumpstered someone should be fired at Lucasfilm.
Where was the scene shot, it had fake sand. I would guess Elstree.
Other than the lightsbaber props and few pieces of the wardrobe of costumes Lucas pretty much held onto everything used in the making of the films except constructed sets. He held onto every last stich of celluloid and every dialogue, and sound effects reel. I know of only one item going missing and then being sold on auction by elstree an ADR recording session supervised by Lucas. I think Featuring Mark Hamill and Anthony daniels doing additional dialogue replacement.
The original globe model that was the estalblishing shot of the death star as the falcon was drawn in by tractor beam did make its way out of the lucas peoples hands. It was recovered from a dumpster. Exchanged hands twice by collectors and thirdly bought by i think sansweet and is back in the lucas archives once again.
You know the story of the deleted scenes not being on the dvd for the movies we like the original star wars trilogy, original indiana jones trilogy. Still sitting in the Lucasfilm archives. Also Deleted scenes from willow, and thx 1138. Instead we got the deleted scenes of the garbage prequels on dvd. And the closest thing we got period for the originals was the CD-ROM and only because the showing of the reels at a convention by sansweet and included at his urging. Done in a time of early digitizing of movies was not exactly up to speed so to speak.