Te Humane Society of the United States recently shut down a large scale rescue group that had predominately Chihuahuas and small dogs. There are other mixed breeds and even a Great Pyrenees. Here is the video:
http://www.humanesociety.org/news/press_releases/2010/07/ca_kern_county_rescue_070810.html If anybody is missing a dog in that general area, I would recommend contacting the HSUS chapter in that area and tell them you are missing a dog and would like to take a look at the dogs pulled from the rescue in Tehachapi, CA. Your dog could be among the group. Good luck.
