The fact that it wasn't updated means that the updater script found some erroneous syntax in the original theme that it couldn't handle, so it either didn't try to fix it, or it *did* try to fix it and after that the syntax was no longer valid.
Or, there is a chance that it *was* successfully updated, and then the syntax changed again and your theme was hidden as it was no longer compatible with SVN.
*quoted from the themesite*
"Older themes
If you are running release 3.6 or a svn build before r26641 you should download your themes from
here."
Either way it will have always been available through the 3.6 cloned/release branch of the themesite.
As I said in my last post, the themesite was was cloned so that the 3.6 release builds could still install themes via RBUtil, and so that people could still download those old themes manually if they were using the 3.6 release.
There's no secret to it, and they aren't hidden anywhere, the "old" themesite is linked at the top of the "new" one.
Also, the updater script you speak of is located in the Rockbox Source, where it's been since it was released.
rockbox/utils/skinupdater/
(you'll need to do a "make" in this directory (assuming you have a development environment set up), to build the skinupdater binary)
I hope this helps.
[St.]