Someone forgot grenade near the lake

On the upper peninsula of Michigan island in the realm of an American tree grows. During World War II, when in the house his parents lived, someone hid on the lake a couple of grenades, well, just in case, and more recently the American discovered this almost 60-year-old caches. He believes that the person who made the caches, or was killed, or simply forgot the place where hidden ammunition. Anyway American claims that the parents do not know anything about the discovery. Loggers will be unpleasantly surprised.