Horse needs a vet but owner wont acknowledge

Hi, I board my horses at a large stable in FL. I have 9 horses, 7 of which are rescues. I fell in love with a black stallion thoroughbred who was dumped there by his owner sometime around April 2010. The horse is beautiful but the owner never visits or anything. About two months ago he developed a limp which rapidly got worse. The barn owner called his farrier to come and look at him and he said he had an abcess. The farrier has come seveal times since then but now says that the horse needs a vet. I am afraid it might be the start of something irrepairable. The barn owner has notified the owner many times but he seems to be in denial and does not respond. I think the barn owner has tried but since the horses owner has not paid him he is hesitant to go too far in to debt for this horse. I tried to contact the owner through a friend of a friend and he has still done nothing. I don't want to get the barn owner in trouble because he did try, but I am hours away from calling the authorities, any ideas or comments would be soooo appreciated. I forgot to tell you this owner "loved" this horse so much he refused us when we offered to buy him a few weeks ago unless I paid him 25K, said he could not part with him because he was sentimental. Just in case this forum is national, I am in Florida. He also has another retired race horse there, same treatment...BTW why the barn owner has not acted to take the horse I cannot say, and the owner owns something like 10 more race horses and he is a neurologist and probably makes big bucks.