There *IS* a cache at the posted coordinates. This cache is only flagged as a "Mystery/Puzzle/Unknown" cache because of the additional logging requirement, as explained below.
In order to be able to claim this cache as "Found", you MUST have found a cache on all 366 days of the calendar. And YES, that does include Leap Day (February 29th). Since the dawn of the game of Geocaching, there have only been three Leap Days (in 2004, 2008 and now in 2012). Hopefully you have found a cache on one of those three days; otherwise, you will have to wait a very long time to be able to claim a find on this cache.
You CAN use previous finds, and it is possible you have already completed the requirements to claim this cache as "Found".
If you have not yet found caches on all 366 days of the calendar but are in the area finding other caches, feel free to sign your name in the logbook and then post a note on this cache page saying you signed the logbook and will claim this cache as "Found" once you complete the requirements.
The cache container should be easy to find. The 5-star difficulty rating for this cache is only because you need to find a cache on all 366 days of the calendar. The actual cache difficulty rating is probably a 1.5. You will need to do some bushwhacking which will be more challenging in the summer months. It wasn't too bad when I was here on February 29th. Be aware of the usual hazards in the woods.
Good luck and have fun!