Oh-no! I am so sorry to hear this- I was hoping for a happy ending. Good luck tonight finding her, and FOR SURE don't give her back to her owner- she just didn't learn I guess. It is difficult to change a cat to being indoors only when they have been used to going outdoors, but it is possible. It takes time and a bit of hassle, but it's worth it. I have had to do it a couple times. Please let us all know what happens!