I caught my roommate using my toothbrush and I still haven't confronted him

So I came back to the hostel early yesterday because my lecturer no show for class again. I open the door quiet quiet and I see my roommate, Chibueze, standing in front of our mirror with my toothbrush inside his mouth. Not his own. My own. The blue one I keep separate from his red one.

I just stood there for like five seconds. He saw me in the mirror and he froze. Toothbrush still in mouth. Then he slowly removed it, rinsed it under the tap, put it back in my cup and said "sorry, I thought it was mine." And walked out. Since then we have not talked. I have been brushing with my finger since yesterday because I cannot bring myself to touch that toothbrush again.

Now I am lying on my bed wondering if I should say something or just pretend it never happened. But the thing is, if he could do that and lie to my face so smoothly... what else has he been doing with my things?