"Lost" can mean (1) you don't know where something is OR (2) you no longer possess something. In the second case you may no longer possess something but still know where it is. For example you lost something to a friend in a bet.
This second case is also somewhat of a nautical term. The Captain of a ship and its Chief Engineering can be standing on the bridge of the ship and the Chief Engineer may report the ship to be "lost", meaning uncontrollable sinking.
Also when a ship is sunk you only have the position of where it slipped below the surface, you don't necessarily know how it traveled on the way to the bottom. More importantly prior to GPS ship position weren't necessarily that accurate. Wrecks are often considered lost until someone has eyes (real or synthetic, ex side scan sonar) on them. Which is what seems to be happening here.