The Violent Vocations songs (once again, not on YT or bandcamp or anywhere I looked)
Omniscient Spine - White Silhouette: This is probably the closest an entry here can be considered lost media so far, because it links to a Myspace page, and that website had a massive data breach; it wasn't on Youtube, Archive.org, and not even on file-sharing services. The only way this could be available is if someone downloaded the file back in the day and uploaded it somewhere, but I doubt it.
Missing links: