@kenncann
In my experience twigs can fall further from the tree than other items. I've had coins and things disappear and then have a twig bounce to a further square. In fact I don't think I've ever seen an item bounce
Try to have at least one empty square for each tree. I don't think items will fall to the back, so have a spot on the side or the front three squares. Also remember nothing can fall on weeds, which can be hard to spot. Especially if you have a lot of flowers.
@Sharpington I'm almost certain I saw an item fall further from the tree when it couldn't fall on one of the close spots. They don't bounce, just sort of fall far. I don't have any weeds in my town really it would just be the items obscuring thing but thanks for the suggestions.