|MadSci Network: Zoology|
This certainly an interesting experiment and you are quite right about their brains.
Cats tend to use eyesight and hearing to locate their prey. Now dogs also rely on eyesight and hearing, but smell is far more important. In dogs, the area of the brain that analyses smell occupies twice as much space as that in cats. Whilst cats do have a good sense of smell, a dog is much better at separating out all the different smells present.
When you hide a treat for your dog, it can find the food by using smell alone. Unless the cat-treat happens to walk or talk, your cat does not have the means to find it except by using previous experience. Therefore, the cat goes back to the place where it expects to find the treat.
This also explains why we use dogs to locate drugs and people.
Try the links in the MadSci Library for more information on Zoology.