Tree Rats

As you get to know me, you will learn that squirrels and I aren't exactly the best of friends. We had a disagreement about the ownership of a couple of sunflowers about 5 years ago and it has been steadily downhill ever since. Due to the ongoing feud, I deem it necessary to cage up most of my vegetable plants. I am currently growing some tomatoes (gardener's delight and peacevine if you're interested, red ones if you're not) in one of my cloche type mini greenhouses with a net construction firmly fastened to the front to prevent the tree rats from entering. I thought it was foolproof until I just went for a stroll and saw a half eaten tomato wedged between the outside of the back of the greenhouse and the fence. There are no visible signs of entry so I'm a little confused as to what's going on. Surely the squirrels wouldn't be so mean as to steal a tomato from elsewhere and wedge it behind my greenhouse, would they...?