Having trouble with snakes

Here's the deal. My mom got me a female rat snake as a birthday present, and she escaped from a zipper snake carrier when I was gonna take her to the doctor. I then bought another one, and my housemate accused me of something I didn't do and turned it loose and wrecked the cage so he has to pay for everything. The one I got as a replacement got caught under the background thing in the cage and was badly mangled and passed away before I got him to the doctor so I ordered another one from the pet store, and it looks like this one might be in bad health because I can't hardly get it to move. They did say they'd replace any pets that were sold within seven days if there's a legitimate problem. Of course they're not gonna consider it a legitimate problem if I buy a mouse and it dies because I feed it to the snake. I'd show a picture of the snake, but I don't know how.