Did the parents really do anything wrong?
The entire plot of Chihiro going into a fantasy world happened because her parents ate food without paying for it. However, the food was just left there. I say that if you do not want your things taken, then do not leave it for it get snatched up.
Is that just a common idea in East Asia? Where everyone is free to leave things where they want without having to worry about it getting stolen? When I was an exchange student in Korea, I noticed that people would leave their bags and computers wherever they wanted and go back to get it an hour later. I would literally see corners of rooms with a bunch of random bags and electronics.