WTF is a proper comeback to someone shitting in your food or pissing in your drink? If this were a restaurant or some kind of function where food is being served, you are saying the appropriate recourse is to up the ante on them, not to call the police, file a criminal complaint, and sue the shit out of them?
This is why I HATE practical jokes and infantile pranks. There is always one (or two) in every group who has absolutely no sense of where the line should be.
This kind of prank is a fighting offense. The only proper 'take it to the next level' from shitting or pissing in someone's food or drink would be to poison their dogs, set fire to their home, put something in their engine to blow it up or loosen all the lug nuts, hobble them for life at the knee cap with a crow bar, or something along those lines.