crested gecko question

Question
We got a baby crested gecko last on Sept 29th.  We were housing it temporarily in a 10 gallon glass tank.  WE have been feeding it repashy.  We have been spraying the tank to keep it humid. We were using paper napkins at the bottom of tank for now.
Yesterday my son said he was holding the gecko and then put him in the tank with the lid all the way closed.  When he came home from school the gecko was gone.  I am guessing the tank was not totally on tight even though he insists it was.  My guess is it climbed the walls to escape although, again my son does not think it was capable of doing that.  The tank was on his rather large desk in his room.  We looked all night for that gecko and could not find it.  Do you have any suggestions about where it might be likely to hide (eg a pile of clothes, under bed,etc.)?  Also, being a baby how much do you think it could have run around?  Do you think it would venture around the house or stay fairly close by?  He didn't seem all that active to us, he seemed to like to hide under the napkins on his tent or rest on the log inside the tank most of the time.  My son was able to hold him and set him on the floor to play with him without it trying to run off.  THanks for any help.  My son is upset and I wonder if that gecko can survive because we don't even allow food upstairs.  

Answer
It's hard to say how much the little guy will move around.  I would set a 'trap' for him.  Put some of his food inside of a rubbermaid tub.  Also put in fake foliage.  Leave the tub turned over on it's side and out in the open on the floor.  He should be attracted to the food and crawl in to eat.  The foliage would make a good hiding spot for him.  Hopefully, he will crawl in there at night, eat and then decide to sleep in the leaves.  They like to climb so offering them some artifical plants to climb on also helps.  They will try to get up as high as possible.  If you feel that he has left the room, set a few "traps" in other spots.