If you have Eco Lifestyle as part of your TS4 collection, you'll want to check the NAP (Neighborhood Action Plans) to make sure that the 'Sharing Is Caring' one hasn't been activated. (I have to admit that I tend to cheat my NAP's in most neighborhoods I play in, because that one allows everyone to come take your stuff. And they tend to start with the higher end stuff first.)
If it's not that particular NAP choice, then I agree with Miataplay that you should post this question in the bug forum.
Good luck with figuring the issue out!