Go to the home page for SFMI and read the reports that are right there. It did happen. Historical records also back it up. Do some DD on your own. It's not hard.
In some parts of the states the ore mined would be termed alluvial which allows for easy break done and separating. War eagle mtn's a hard rock show and the old timers took the visual only [2 oz plus] and in the process left tons of grades that can be processed economically by SFMI