fluffy, i often have the same problem. i 100% of the time put my char's in their houses at the end of the day, yet sometimes they end up just outside the house, at market, or the odd time somewhere else.
then sometimes it clues in to me... ghosts! no, just kidding... sometimes i probably sign out before that final click (into the house) actually takes place. other times i'm playing one char... then need an item. so i get my other char out, sell that item on market, then go back and buy it on the first char. when i'm done playing that first char, i log out. and would you believe it? my second char is still in the market, even though i always go home when i'm done fighting.
mistakes happen... memories sometimes slip. that's life.
--jason