It also doesn't really mention how this “lost” material was identified. If you just subtract the encoded from the original, then any phase difference will make it sound like material “disappeared”, while in reality, it just came very slightly earlier or later.

I guess it was exactly as you write - but instead of slightly earlier or later, the "lost" sounds are the high frequencies (a lot of hissing, clicking etc.) - the actual sound is mostly still there, but slightly "muffled" because it contains only the lower-frequency components.

It's 128kb. The useful and informative article is mentioned at the end: http://theghostinthemp3.com/theghostinthemp3.html

If it's really the original MP3 version of Tom's Diner produced by the Fraunhofer engineers, probably not a very high bitrate. Aside from that, I would say that even back in 2015, MP3 was already on its way out and replaced by better (while still lossy) compression methods?

With space not much of an issue anymore, FLAC is pretty much the default nowadays. And even though Opus and AAC and others have better encoding than old MP3, but I guess a 128 Kbps MP3 encoded in the original Fraunhofer l3enc (the best back then) and one encoded with LAME will be different - and the LAME version will be "better" because of improvements in psychoacoustics? At least I remember l3enc being MUCH better than anything else at 128 Kbps (Xing lol, cymbal washing anyone?) before LAME came along.

> With space not much of an issue anymore, FLAC is pretty much the default nowadays

The default for what? Space is not the only consideration. What about bandwidth?

I'm pretty sure spotify, deezer and the others are not transmitting FLACs, especially not at the base quality level.