Just a little note here before you ask how is this in "existence unconfirmed", if it's partially found.
From The Lost Media Wiki
I also put it in existence unconfirmed because we don't really know what these SID files were for. Adam Gilmore has gotten up to say that he himself doesn't remember anything about those SID files. I've made a few theories about what these SID files could come from, but until then, it's a mystery as to what those files were for. Maybe those SID files are all that exist of Mad? Who knows?