Have you tried out any classifieds site? I do not know which one but a friend moved in with a few people found that way, pretty recently. I believe there are plenty of classifieds available where you can browse via location to narrow down.
Where did you leave them?
Have you checked behind the sofa?
When I was looking for my roommates, they were usually hiding in the spare room.
If you don't have a spare room, try leaving a saucer of milk on the door step.