That article isn’t the most reputable source for lost Fantasia material. Unless there’s citation-- and sadly, there isn’t-- then it’s just hearsay.

The original sound stems aren’t “lost,” that would imply that someone’s just unknowingly keeping them stored away in their attic, basement, or storage room somewhere. They were nitrate 35mm film reels, which have a horrible reputation for either deteriorating fast under bad storage conditions, or bursting into flames that even water can’t put out. You don’t even have to look further than the film’s 2000 DVD “making of” featurette for the following factoid: no more than 12-14 Fantasound prints were ever manufactured. All but one of those prints were junked, which allowed a 4-track magnetic copy to be created via then-high-quality RCA telephone wires. That’s it. That telephone wire transfer is all we have left today. The first generation nitrate stems, which contained Taylor’s complete commentary segments, have sadly been lost forever to time.

The magnetic stereo soundtrack and reprints of the 80min RKO cut contain all that have survived of the original Taylor commentaries. Several preservationists have already made efforts to capture the mag stereo mix (in fact, I have the 1969 release on loan from a very generous collector and I intend to have it preserved as soon as possible), so we can rest assured that that mix will surface in decent quality soon enough. Locating a good reprint of the RKO cut is the real trick.