Granted you have spent this much time and effort with this person, but knowing that the seller is no longer interested in selling the animal, pushing is really not going to get you far in terms of getting the animals in question.
Putting it on the BOI is out of the question, really. You did not exchange funds, and although you were told that this was the deal, the person in question does have a right to do what they will with their animals, and you will be told that ad nauseum if you post it on the BOI.
I think you should move on with your money, and make sure to note that this person does not deserve your funds from here on out. There are plenty of other fish in the sea.