my first time coming home to a empty tank....hellllllllp!

I live in a 2 story house.

downstairs = laundry room, dining room, living room & kitchen. one 1/2 bath and a stair case...all my doors are sealed so I know she couldnt of gotten outside. i looked behind and under the couch and all over the rooms, also looked behind the washer and dryer, under the stove and behind the refrig.

any clues on where they like to hide? and is it possible she would climb a flight of stairs with a double landing?

crap crap crap....