I've searched both of the bookcases and could not find either. I tried every book. It said that the secret compartment was empty. So I went to my bank and could not find either (or the star amulet). What am I missing here? I have the gardener's head in my inventory.

P.S: I started this quest a while back and just recently picked it back up.

 

But still, there should be a way to get them back??

Read your quest journal, try to match it up with the quest guide and see if you missed something. If you dropped/lost an item you got previously, you'll have to go back and get it (and find what it is).