I wish I lived close enough to help look for it. If you haven't checked these areas, give them a try on your next visit...
I took a look at the topozone maps of the park searching for Cave symbols (which look sort of like "--<"). See the following link for the real symbol...
I didn't see any cave symbols with no names, although scannign a topo for these symbols is tedious at best. Keep in mind the coords were obtained by simply placing the cursor over the tip of the cave symbol, so they probably aren't completely accurate, but should get you close enough to notice a cave entrance.
> Unfortunately, it's still a mystery. Went searching this morning and > am sorry to report that I could not find the cave