Sorry, I didn't see any of your replies until now...

I contacted several rescue groups but none of them replied to me. So I talked to the lady that comes to Petco all the time and runs Australian Shepherd Rescue. She can't take in any more dogs, she runs it from her home. She said that most of the groups around here don't take owner surrenders.

There is a board at Petco but it's for Lost and Found pets only. I've asked co-workers and friends, but nobody wants him.

I sent an email to Coco's owner telling her what I found out but I haven't received a reply. I don't know if they still have him or not, otherwise I'd try the classifieds at Petfinder.com