Hmm, one time one of my girls went into our bedroom closet and went under the laundry hamper. It took me two hours to find her and that house was only 400sqf on the first floor!
Typical places are under furniture, corners, behind electronics...one of my friends beardie scaled a curtain and ended up on top of a shelf. If you have clothes/towels/blankets and such on the floors be sure to look under those too.