or do the same with water, cornies drink quite a lot, so put some bowls of water around the tank area on the floor, it should come out for a drink, they are most usually active at dawn and dusk, so should not disturb your sleep
How is it fed normally, is it in the tank or a separate box? Mine are fed in a separate box that they have the scent of, so this might be another trap to lay for it as it may go in there thinking it is feeding time.
Are clothes or other like materials stored close by on the floor or on a low open shelf? Boxes and stuff like that provide a good hiding place for snakes, where they feel warm and safe.
Final thing is don`t panic, i know this is easy to say but generally it will stay out of your way as they are quite well predated in the wild and tens to seek shelter and lay low than slither around the place. They are not venomous and have gentle natures which makes them good pets.