I have entire albums in my old iTunes library that you literally cannot find online, anywhere. Hip hop beat tapes that were uploaded on a music blog in '07, and the blog was behind a Blogspot adult notice and so it never got archived. Or old PHP-based music forums that did URLs via query param, which only ever got their homepage archived. Old James Blake demos from Dubstepforum whose Rapidshare links have been 404ing for 15 years.
The pace of bitrot is freaking crazy!
Even my library is not what it was, I had two drives fail on me the same day in college and I lost over 100GB of meticulously-tagged 320k and FLAC files.