Is he using the litterbox in your room? If he is, then perhaps he just needed some quiet time. And if you suspect the other cat is the one doing the peeing, perhaps he needs to be checked by the vet as well. Its the least you guys can do to try and save Joey! It could be something as simple to treat as a urinary tract infection. I hope you can get both of them to the vet soon to be checked out, before your mother makes you take him back to the pound.