First I want to say I am sorry this happend to you. Then I want to say I had a simaler experience but from the other side of the fence. I had a litter of puppies (beagles) had found homes for all but one, I thought. So I advertised the one boy puppy, I had probably 30 plus replies. I sorted the first twenty, found three great people and chose the best one for him. I replied to probably half the others saying I was sorry but the puppy had already found a home. Then the people who had reserved one of the girls (the first pick even) called to say that due to medical problems they wouldn't be able to take the puppy anymore. So I emailed the rest of the people (this was three days after the original  posting) I got some nice replies back, and one ticked lady who made sure she first told me how wonderful her home was and how much she wanted the puppy, then said BUT we found another puppy since you couldn't be bothered to email me back and tell me he was taken. She called me some names, said I was rude etc. I should of left it at that, but I didn't I replied back that I was sorry I hadn't gotten back to her, but had over 30 emails and that I just didn't have time to respond to them all. I also said I was glad she had found a puppy and that honestly if she couldn't wait 4 days I was glad  she had not gotten our puppy as honestly if you can't wait four days, you are just buying a puppy on impulse and that is NOT the kind of home we wanted for our puppies.
I hope you find a beautiful dog. I do agree though you get what you pay for, usually. I would be very leary of a  free purebred puppy. I don't really care if a dog is registered with the AKC, CKC, UKC etc. but if it is free there is usually a problem with it, or its not actually a purebred. I rarely even see mixed puppies for free around here.