I think I'd contact any livestock sales you can find including that 'Price Horse Sale' place, with info about the horse being stolen property, under investigation with the DA and Sheriff's dept, NOT saying the name of the suspect, but maybe saying something about not being able to give the name due to current investigation etc. (don't get sued for slander or liable, besides how likely is it he'd put it up for sale himself.) A picture of the horse, a complete description of him, and some info about the situation so they will hesitate to allow it being sold, and might even contact the police if someone tried to sell it.