Had it been found and reported in England they and the landowner would get a significant reward. Of course, it is not possible for a find made by a group to be kept quiet. I wonder how many coins found by individuals do not get reported because there is no real reward and the finder would rather keep or sell it than get a "good citizenship certificate"?
If I were to spot such a shiny gold coin on the ground my first thought would be that it must be a screw cap from a wine bottle. Amazing find.