Whether you thought you heard something or just wanted to be cautious doesn't matter now. It turns out listening at the door was not the best choice available to you, for at the very moment you set your ear to the door - entirely coincidentally or was it? - your kindly neighbours had themselves set to the task of saving you from self-imposed entrapment... by hacking down that same door with an axe! The heavy head shattered the thin wood readily, and continued through with violence, cleaving your skull in twain.
Fortunately for you, all you experienced was a second of brief confusion followed by nothing at all.