I think "Missing" is a pretty poor choice of word for this; "Presumed lost to history" would better explain what's happened - Which is both incredible and terribly dull at the same time! Somebody connected the dots on the provenance of a quite old painting that was venerated, but perhaps not as much as it should have been, not far from it's last known location - At least in distance, if not time. Great detective work, and far more interesting than if it'd been lost or stolen and people were looking for it - This was a piece that people knew existed, but nobody was looking for.