Jenny23 is right. Even if the place in the store is full, you can still return an item. Maybe you bought too many candys and you need some room for food. You can just click on the item, drag it to the store and it will ask if you want to return it.
Also, if you buy home-repair products, you can set them down where they are to be used, even if you don't want to use them yet. I've had a bucket of compound sitting on the porch for ages!
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If I can get them to think, I'm half way there...