What is a Yorkie puppy supposed to look like?

My mom went and bought a supposed "Yorkie" puppy that is 13 weeks old. From all the photos I have seen on the Internet, this puppy does not look like a Yorkie. He looks like a mix of some sort. Almost like an Aussie terrier. He is black & tan, with sort of perky ears. His fur looks feels very fine & dry. He is very cute, but to me, his snout looks too long to be a Yorkie. Yorkie's are supposed to have sort of flatter muzzles, right? I am no expert. Any advice? The people my mom bought him from won't answer the phone, but my mom said that she saw his parents on the premises. I still think he is a mix. Should there coat be that thin & wiry feeling?