Right under their feet!
In Tonopah NV there is/was a silver mine for many decades. The richest part of the vein was on the surface and intersected the road that all the miners used daily to get to and return from the mine shaft. It was only discovered after the mine was closed and is still there to this day.
Like you say “in the box”.
One day I saw a strange rock that looked like quartz but was egg shaped. I picked it up and brought it home and forgot about it. My little boy was about 3 and reading his dinosaur book and said that egg is just like daddy's egg rock. Closer inspection revealed that was exactly what it was. I rushed to ebay to see just how rich I was. Proud to say I could be as much as $15-20 richer if I ever sold it.
Many years ago when the oil patch was slow, I was working for a geophysical survey outfit, ‘stomping’ and picking up jugs (geophones). While picking up a string of geophones I found a ground stone axe head. (Someone had walked right over it a couple of times while putting those geophones in place.)
“It really is amazing how so many people are “in the box” to the extent that they can walk buy an extraordinary historical find, and never see it.”
And then there are people who see things that aren’t there:
http://urbanlegends.about.com/od/humor/a/barbie_doll.htm