Actually most cultures don't bury their weapons in times of unrest or war. It's possible that what they have is the remains of someone's peace ceremony - burying the hatchet.
“Burying the Hatchet” was my first though as I read the article. I was taken surprised at the idea that someone would bury their weapons during war and then lose them.
Perhaps it was the first “ weapon buyback” program. For each sword, axe or spear, you get x amount of grain or some other commodity.