The quest is not bugged but it is indeed a bit tricky. When you first enter the cave look for a datachron on the floor at end of the tunnel just before you enter the large room where the Sargent is...when you find it head over to the Sargent where the second datachron is...Follow the tunnel left of the Sargent until you enter another large room then on the left nearby look for another datachron...then go up the stepes across from the tunnel and then go left to the room with the box but before you go in at the entrance on the left side in the bush is another datachron...when you find it proceed to the box which should now be glowing and interact with it...and you're done :D

You can find them by following the second available path to the left when you enter the cave. They are hiding inside a box on a corner. However, the quest seems to be bugged as it does not get completed (14/06/2014).