This is a sad story, but you got a cool piece out of it. The critters tend to eat the poison and run off to die in little nests of their own making. You probably won't find them unless you do a very thorough cleaning.
We have a lot of mice and rats here (outside, not in the house) and we have done many things to get rid of them from our cars (they chew the wires). But not poison. We have sprayed peppermint, as they can't stand it, and we have beeping devices in the car. Now we have bright lights that shine under the cars all night long. So far, it's working.