It is definitely not lost at least not the source of the Amiga version. I am the coder who ported it (commercial port based on a license) to AmigaOS back then. At best ny knowledge the company for whom i worked back then still fot the source. Not sure if they kept the unmodified Windows-versions source though or only the Amiga-version’s source.
But it is correct it was never publicly released, the source code. Possible that the source of the Windows-version is lost.
MagicSN