When we have gone through this hiding experience I found it best to just go about my daily business and not let them pick up on any stress from me. One day he will just come stolling out like nothing had ever happened. As long as he's eating some and using the litter box I wouldn't worry. He just needs to do it on his own terms in his own time.
Keep us posted.

Come on out from under the bed Cubby and make momma feel better!!