If, and only if, you have the quest requirements(not the needed items), and you stand on the center of the Zarosian design under the Digsite, then, and only then, will the quest begin. This is what happens when you stand on the proper spot. Abruptly, a cutscene begins. The camera spirals upward, showing you stand there, then suddenly clutch your heart and collapse. Everything goes black. You wake up in jail.