His owners claimed him..
They had pictures of him from age 2 weeks (from the breeder) up till right before he was lost..
Like I had thought, he got out of their car, and they didn't realize it. Their daughter is 6, and they said she must have left the door open on the car a little too long, and some how didn't realize that he had fallen out.

They didn't seem like the best of owners, but I couldn't keep him from them since it was obviously their dog..
I really do miss him.

His name is Mason, and he is indeed a yorkie/chihuahua mix.