Oh I would have been soo mad if that happend to me!! I can totally understand what your going thorugh, I hate it when my roomates take stuff without asking and pretend that it just "magically got used".. GRRR I would complain to your landlord right away. Tell him/her you dont feel safe living in the same building as this freak!!.. You have every right to say somthing, not only as a mother, but as a resident.