Yes, I think you are over reacting. Mine that are grown can sneak into a room when I go in or come out and I never know they went in until I hear them crying to come out. This one you said is small so she could have slipped in easily un noticed. This happens to all of us and one day it will happen to you (if you have a kitty in the house). You think nothing of them being gone for hours at a time because they go off to their favorite hidding place to sleep and won't answer or come when called until they are over their nap. It is just a easy thing to accidently do... couldn't tell you how many times Chester has been shut up in the closet....