Sometimes.. really late at night.. i hear dueling banjos playing in my head
But seriously.. if it's just a one-time thing i dont think you have much to worry about. It could just be your subconscious playing tricks on you. Sounds like you were a little depressed and maybe stressed and also tired, that combinaton can be hard on your mind/body. Strange stuff happening under these circumstances wouldn't be unheard of.
Taking a day off for a small relaxing vacation can work wonders.