OK, nevermind then, I just went to see his pictures and looked at your post and noticed there was talk of a different puppy. No worries
He is a doll though and I noticed he weighs a lb now. Dang, I was a good guesser LOL. I would be willing to bet he was sold earlier and told an older age so you would think he would be a tiny when full grown. I am sorry you were lied to, more than likely the paperwork would have shown him to be much younger and by giving you an outrageous price for papers she figured you would just say no thanks.
Again, all of this is just my speculation from all the info I have learned from the wonderful people on this site.