I don't think Groovin' Garrett and I are in any real disagreement. Except for the Motown stuff: I was told the "discarded masters" story by one of the Mercury mastering engineers who, when he worked for MCA, had been tasked with making shinola from the sh*t, as he put it. I would like to know more on the subsequent history (that's not a "prove it!" challenge, I just like to know this stuff). Now maybe some of the higher-quality items turned up subsequently, and as I said the Rhino people happily pointed out that the recording engineers kept high-quality dubs of mono masters, so good source material existed, and now it is being used. So far so good.
The Atlantic info I got from one of their box sets, and I'm not surprised some of their masters were stored elsewhere, but certainly the session tapes are gone, hence no Coltrane or Ray Charles outtakes beyond what was located elsewhere.
I never said "Tommy" was lost, I said it was rumored to be lost, a rumor started by Kit Lambert himself back in the day.
If the "Days of Future Passed" mixdown got damaged, I can see the choice to remix, though as you say if there's a good safety dub they could have used that. And if the band prefers the remix that's fine, just be aware it's different from the original LP. Which it is.
Yup, in agreement for the most part, Doc.

VERY few Atlantic multis exist. Very sad indeed.
Both the master and US safety of DOFP exist and are playable...it's the Moody Blues that keep the remix as the status quo.
As for Motown, a reputable source at UMG had told me that 90% of the mono masters were intact, and were being used for the Complete Motown Singles boxes. Doesn't mean it's gospel in any way, though. Anything's possible!