What's the return policy on a cat?

So the 4 Sewall mice are at it again. I spotted one in the living room last week and last night one scurried past Scout in my room to run over my feet in the bathroom. AWESOME. I fear that our bugging the maintenance crew to seal up the holes on the outside of the house has sent them to seek refuge inside the house. Of course, when we had a mouse problem back in September we tried everything to get rid of them. And we finally got a cat. With big paws. I even researched it and read to get an adult female, because they are the best at killing mice. I was also told by my classmate to not get a kitten because they don't chase after the mice and will grow up becoming friends with the mice, as her kittens did. Who knew she would be a dumb cat too. I think these mice even scare her because she keeps jumping with every sudden movement. Pat's suggestion is to get rid of her and get the most ferocious looking cat with scars on her face. Now that cat would kill some mice! My mom asked me today if it was a mouse or a rat that ran over my foot, but I want to assure everyone that it was a little mouse that ran into the bathroom. And of course, each time I've seen a mouse I start screaming for Scout, and she just scrolls over to me and gives me a look as if to say, "What, you want me to chase a mouse and risk breaking a claw?"
Here's a picture from last night, only minutes after my mouse encounter. She's just sprawled out next to me on my bed, looking as innocent as ever.

Anyways, I would like to reinstate a weekly dinner night. Let's make that happen.