I just found a "bouncing" gps cache this weekend that was quite obvious even without a bit of plastic showing. It was in a neatly stack of wood/sticks with a open firepit nearby. If it isn't found by a geomuggle this summer, I'd surely be surprised.
A lot of my finds were as easy to see as this. Off trail a bit and into the woods, you'll notice nature does not pile their sticks and leaves quite as nicely as the human tends to do...
Silva, of the forest
Beneath you, feel the Earth.
Above you, feel the Sky.
Around you, feel the presence and the Power
of the Trees!