1408 has 3 different endings. the one where he actually gets out, gets back together with his wife, and the room is destroyed is a happy ending. the daughter is still gone, but at least he's come to terms with it and destroyed the room.
the room itself was haunted and could bend reality. it wasn't just that it was altering mike's perception of reality, though that was happening also. i think the room was actually changing and would change back to "normal". so, when mike recorded things, i think the room had created an actual copy of his daughter to talk to him.