Can I change my lock if the super steals items from my apartment?

One day I came home and a item was misplaced, I thought nothing of it because I thought I might of misplaced it and didn't put the item back. A week later (today) I find more items misplaced and my camera missing. I checked the windows so there was no force entry, so the person who came in to my house had to have had a key and the only people that has my key is my mother and the landlord. I know my mom didn't do it which leaves the landlord. The super is constantly in the landlords house because he is elderly and he needs help all the time. My theory is the super took the key from the landlord while he wasn't looking and he entered my house and took my camera. What should I do???