An Oyster and a Pearl

An oyster saw a loose pearl that has fallen into a small crack in the ocean bed. Painstakingly she retrieved the pearl and placed it on a leaf near her side.

She knows humans search for pearls and thought, "This pearl will tempt them, so they will take it and let me be."

When a pearl diver showed up, his eyes were conditioned to look for oysters and not for pearls resting on leaves.

So he grabbed an oyster which did not happen to have a pearl and allowed the real pearl to fall back into the crack in the ocean bed.

We know exactly where to look
That is why we fail to find what we seek