I don't konw what day of the week westcoastJTF makes the backups onto his website.
But if you label d.mp3 as a.mp3 or b.mp3 then they will probably be backed up.
I don't recall what a.mp3 and b.mp3 were but it looks like they are not made anymore. So I guess westcoast's script doesn't see them and doesn't back them up and just backs up c.mp3
better if the filename is consistent with whatevr a.mp3 or b.mp3 were