find your hamster during the night because the chances to see it
awakened are higher. Be sure he/she can't get out of the house and that
there aren't other animals that can hurt your hamster that escaped. If
you hear any strange noises in a room, close it and search your hamster
there. Put some hamster food (specially fruits or food you know he/she
loves), water and a nest in a box, in a way the hamster can enter it,
but can't leave it. So maybe during the night he/she will enter it and
sleep there. In the morning you'll be able to find it there.