What a cutie! Can you keep her if the owner is not found? I am sure you have thought of scanning for an ID chip. Was there even a collar on her? Please let me know if the owners are not found, I am a lover of Chihuahuas and will try to help.
I think Randy looks like he's found himself a new baby. She is adorable. Peggy Mall has 4 Chi's but I can't remember if she had a brown one. I can't imagine it would be one of hers though, she keeps them close to her heart. I'll ask around.
Keep us posted!