Sift

Sift - to sieve (sand, flour, etc.) in order to remove the coarser particles

After finishing sifting through all the available hypotheses, Mellek was left with such a bazaar idea that he could not believe it was true. But he suddenly remembered that Sherlock Holmes used to say: "When you rejected every possible option, what is left is the answer." Or may these were not Sherlock Homes's words.

Frank stood and cold water was well above his knees. He bent down and plunge cradle into the muddy waters and lifted a heavy burden of wet soil from the bottom of the stream. With a long sigh the man started to sift the content of the cradle intensely looking for the sparkle of gold sand or, if Lady Luck was in a good mood, of a small nugget.