Horse crisis: a.k.a. why I'm here.

I bought a horse back in 2002 named Whisky. He was amazing, spectacular, phenomenal, and any other positive adjective you can imagine. I boarded him at an old "ranch" called Fredrick's until it shut down in the end of 2003, and then moved him to Cottonwood Riding Club. He remained at Cottonwood-- fully paid for-- until August of 2007 when I could no longer afford to fund his stay. Cottonwood then offered to put a lean on him, so that one day I could pay his debt off and provide for him once more. For the last 2 months I have been blessed with a helping hand who is offering to help pay for his return, so we set off to purchase Whisky back from Cottonwood. Both parties agreed on a price the proper payments were made. However, when I went to go pick Whisky up to trailer him to a different stable (Cottonwood did not want Whisky to still be on their property) I was informed that Cottonwood had not yet cashed the check, so I could not leave with, or see, my horse. Six days later, I was informed that Cottonwood had actually sold Whisky in an auction, and had tried to sell me a different horse (my Dad's ex-horse, Buck) instead. Whisky is branded. We still have all of his papers. I need to know if there is anything illegal Cottonwood did that I can either sue them for, or another way to get my horse back: i.e. tracking down the buyer, or anything else. I need Whisky. Please help!