sherry,
If you know what county they are in, I would call the Animal Rescue authorities there and report their information. They should be able to track them down either through the sales website, or their phone #. They should definitely have charges brought against them for animal cruelty. If nothing else, the horse (and all other animals they probably own) will be rescued and taken care of until they can find a home for them. I just hate to see defensless animals suffer at the hands of someone who could be so irresponsible.