What should I say to my roommate from last semester (who stole my stuff)?

He stole my stuffed Kermit the Frog. I know it was him. I know that he was capable of it since he also stole someone's iPhone.

Yet when I see him, he's still just like, "Hey man, how are you doing?" and pretending to be my friend. What should I say to him?

"Where my Kermit n*gga"