I thought 1999 was the release of "Stormy Weather".
"Stormy Weather" was released in 1998. The "1999 TWC Music" cassette contained the final set of music they composed.
Why does an Artist make their music unavailable? It makes no sense to make the music unavailable so new listeners can't get it.
Artists don't "make" their music unavailable. Publishers just stop publishing them when they can turn a profit. Making CDs isn't free, you know.
However, I don't see why they couldn't have made their recordings available as mp3 downloads (unless the masters are gone).