It is hilarious how well we all relate to this problem!!!!
My daughter would come home from college for the weekend and shop through our cabinets for shampoo, toothpaste, etc. (even though we gave her a stipend for those expenses). It never occurred to her that it wasn't appropriate. After all, it was "her" house too. We had to have quite a "talk" about it. I would like to say it cleared the problem up....lol
We still love them.......anyway, but it is still quite frustrating!