What happened to Adam? He was not in the cage with the devil when Sam went in to speak with him! Where did Adam GO!

Either they couldn't get the actor back to portray Adam again, یا مزید likely, the writers have just forgotten about him. He was just a plot point for season 5 and then got ditched.

Rowena Transfered Lucifer into a different cage which is why we didn't see Michael/Adam