Ranch Pony Cyndi Constance Sold me a lame horse with the wrong description Houston Texas

I bought a pony from Cyndi Constance/Ranch Pony as a riding and jumping pony. They told me he had been a cattle horse up in Wyoming and had bought him and brought him home in October. He moved perfectly fine both when I tried him and when I brought him home. I flexion tested him and he was alright. After 6 weeks or so passed he started going increasingly lame until two months later he couldn't be ridden again. I brought the vet out and had him x-rayed and he said he had extreme arthritis in both fetlocks in a place where injections would only work for 6 weeks as well as a bone chip. He suspected that the pony had been injected right before I tried him and it wore off after 6 weeks and as I increased his workload. He had to be permanently retired as a pasture pony.

I was extremely suspicious after that and started digging into the internet to see if I could find information. I found a horse auction up in North Dakota in October that had a horse with the name and a picture of the horse on their website. Exact match. The description of the horse named him an Amish cart horse and 2 years older than they told me. Considering the hard use of Amish horses on roads it explained the severe arthritis. They had to have known when they  brought him home that he was dead lame. They had obviously ridden him all over the property while lame before selling him because he was used to the trails I rode him on. I couldn't get in contact with her again. 

I'm very upset because I loved that pony. He was so good natured and pretty. Everyone who saw him fell in love.