I think some of these tips may be useful, :
* Remember that hamsters are nocturnal, so will probably only move about overnight.
* Place a small pre-counted pile of sunflower seeds on the floor in each room. If any seeds disappear from a room, that gives you a better general idea where your lost hamster is hiding (unless you have any wild mice that are stealing your bait!).
* Sprinkle a little flour or cornstarch on the floor around the piles of seeds. A trail of little white footprints may lead to a hamster's hiding place.
* Similarly, sprinkle some flour across doorways and in front of any suspected hiding spots (like spaces under the cupboards or holes in the wall, as noted on your search). Check for footprints to see where your hamster is travelling at night.
* In the evening, try placing tinfoil or crinkly cellophane on the floor (concentrate on possible hideouts, doorways, and around the cage or food), turn out all the lights and sit quietly. If your lost hamster comes out, you may be able to locate it by the noise made as it walks across the foil or cellophane.
* An ingenious owner sent me this tip: tie long strands of yard to some peanuts (in the shell) - your hamster may gather them and take them to his or her hiding place, in which case the strands of yarn will lead you to the hiding spot!
I hope you find it soon.