Help!! I just purchased a lame horse?

was looking 4 a safe trail horse.Found him in NY state.I went up to visit him to trail ride & he was great but as soon as I got him in the ring he was off on his right.I was told that he had sat for a year & this was the first time they had seen himoff.He seemed to be great onthe trails, went through water, etc. what I was looking 4. I went back a 2nd time & trailed him again &he was fine .Put him in the ring & he was off, had a hard timegetting him to canter,etc. they told me that he had not had shoes & had a farrier come in & shoehim & that was t heprob. I really liked his personality.I hired an outside vet to do a pre-purchase exam. I requested x-rays. After a 20 min conversation with the vet, he ured me that there was absolutely nothing wrong with him & felt it was a waste of $ to xray & he was fine.Got him home & he was off .had my vet xray him here& found he had a fractured coffin bone that didnt mend correctly . Any sugg,what can I do? I now have a 3500. lawn ornament.HELP