give the little trigger some time to get used to his surroundings, and the surroundings outside of the tank. also, a tankmate wouldn't hurt. my niger used to hide all the time, then i threw in a huma, and he's always out (mostly being greedy with the tank and making sure the huma doesn't go in HIS little caves).
it's so funny, the huma will do all this work to excavate inches of sand from a small opening of a rock to make a nice entrance to a hideout spot, and then my niger will come bully him out, and claim it for his own. i think my niger now has 5 caves he defends, and hasn't put an ounce of work into any of them. poor huma.
ben