VocaDB says it was on a compilation album that was originally free to download, but that seems to be lost too. I was gonna say it's quite strange when this happens (because everyone likes downloading and sharing free albums, and in the Western fandom, plenty of Vocaloid albums make their way to YouTube eventually), but knowing how popular lost media has become over the years and hearing about other internet works that were previously easy to access until they weren't, I guess I shouldn't be surprised that some obscure works become lost to time once their download links expire.
I'm now going down a rabbit hole on VocaDB's partially found and unavailable tags lol.