Asking nicely will not help as indicated by the fact that the organisers have stated that they have referred the matter to their lawyers. Instruct an attorney who will look into the merits fully and advise you. Generally speaking and not knowing all the facts, your attorney will ask the organisers and the owners of the resort in writing to identify the owner of the horse. When they refuse/fail to respond/deny all knowledge, sue the organisers and the owners of the resort jointly and severally, the one paying the other to be absolved. They will identify the owner in their pleadings or risk judgment against themselves. Then join the owner to the action. One is legally obliged to maintain control of one's animals at all times and failure to do so attracts strict liability. Be sure to claim for future medical expenses. This is very simplified but your attorney can advise you more fully. Good luck.
