I managed to 'lose' my rescue cat on the 4th day after adopting her...
I could not find her and then realised after searching the whole house over that the only possibility left was that she found a tiny space in the utility cupboard (I had closed it but somehow she had managed to open the door) where there is a tiny hole behind some pipes the gives access to the floorboards...
I was beside myself, crying and went all the worst case scenarios: ''cat is stuck under floorboard, cat is going to die under the floorboard, cat is going to hurt herself touching a wire or a boiling central heating pipe, I have to call someone to rip out the floorboards right now, cat is going to find a way to get into the neighbours' floorboards...''
In the end someone told me to calm down and just put food near her hiding place and the cat finally finally left her hiding hole tempted by the food. She was perfectly fine...
My point is cats are masters at disappearing and reappearing. Put food out as people have already suggested and try not to worry too much.
Mine has also hidden in wardrobes, drawers, cupboards, the laundry basket and made a nest behind the bottom of my bedroom curtains (took me a while to spot her there and again I thought she had disappeared).
Fingers crossed yours will make an appearance soon.