How to find an artifact in the third mission ??? (United Assault - Normandy 039; 44)

How to pass HER ... in the third mission in some castle you need to take an artifact, I've already replayed a couple of times I go to the mark on the map there is an Armored Personnel Carrier ... But there is no Artifact ... I crawled everything, even blew up an Armored Personnel Personnel, there is no artifact, and Further you can't go through the game, there are no missions, but you can't finish this mission without an artifact ...