This.
It's like asking "if a tree falls in the forest and no one is around to hear it, does it make a sound?"
Or, if u want a different answer, you and me °-°
Edit:
You - cause if the room has no entrance etc and you know how many people are inside, one of them must be you.
Me - cause if you are telling it to someone, that person must be inside the room with you.
Only you and me - cause you told that you aren't lying and so there are only 2 inside °-°