Partially inspired by the "This isn't what I ordered" thread, and partially from discovering where it was my boy hides, lets hear about unusual hiding places for our precious masters and mistresses cats.
We all know about when they try to squeeze into boxes that are far too small, and my girl often tries to get into the very small cat cave on the tree - she ends up with head and bum sticking out of the doorways.
But my boy, who is much shyer, prefers behind the sofa. He did have a habit of squeezing under the recliner (only part with more than half an inch height), but today he vanished completely & clearly wasn't under there. Then I worked it out - there was a suspicious bulge in the back of the sofa itself. The backs of the non-recliner sections of the sofa are like flaps that Velcro at the bottom, and he's somehow squeezed himself between the flap and the frame! 
Sort of my fault he went there - he's awfully untidy with the litter tray & had walked it everywhere round the room, and I got the small hand vacuum cleaner out. I do that every weekend, but he clearly hasn't got used to it yet & today panicked completely when I turned it on 
. I do hope he can get himself out OK, otherwise he will panic even more if I have to move it away from the wall to help him out.