Here are a few of the trickier hiding spots that I have come across:
...Inside a key carrier that looks like a rock...
...Inside a corner post, under the cap...
...Inside a plastic barrel cactus...
...Inside a rubber black widow spider...
Many are buried under rocks, tree branches, who knows what! In time, you may, as I have, come to hate micro caches. The sad part is, you will still hunt them. You just won't log your DNF's as much.