You got to hand it to them: The is an epic dumbass goof. The piece in question is Picasso's "Woman's Head" painted in 1939. It was stolen from Greece's National Gallery in 2012. At :22 seconds, you can see the painting being presented for the press when the damn thing just slides off and hits the ground. Nice work, gumshoe.

Also recoverd was "Mill" a 1905 painting by Dutch painter Piet Mondrian. No clue if they dropped that too, but I'm just going to assume.