This is allegedly how the Paris jihadists got their weapons, including an RPG.
And there have been lots of weapons from WWII floating around for decades: a lot of German ammo dumps and supply depots were just bulldozed over by the Allies after WWII, allowing an enterprising man with a shovel the possibility of recovering a lot of weaponry-- if it was packed in cosmoline, it's probably still in good shape.
A couple of years ago some guy in Berlin was arrested for trying to sell a restored Bofors 40mm anti-aircraft gun and some MG42's he had dug up in prime condition somewhere. With ammo.
I would love to have an MG42.
CC