I can't think of a bowl that would stop them from digging them out or some type of set up. Hmm do you think he wants the food lower? Is he digging it out and then eating it off the floor? You could try a dish that is low to the floor and see if that stops him from wanting to dig them out.
Other then that, I would get a small broom and dust pan and sweep them up and put them back in the bowl so they don't waste them. But if you have a wire bottom, that won't work because they would fall threw. Though if that is the case, may be you could put a small piece of tile or something under the bowl to stop them from falling threw the wire so that you can put them back into the bowl.
I will keep thinking and see what I come up with.