-He didnt give you the correct amount of money for vet fees etc.
-He NEEDED the horse that minute
-Wanted you to deliver it
-Never even saw the horse in person
-And his daughter didnt know what a lunge line was (that would have been a big enough deal breaker for me)
I don't mean to bash you but there were lots of red flags. The second I would have heard a goofy email from that guy I would have been done with him, I don't understand why you let him be so pushy with you. YOU were the owner of that horse. Things can be done on your terms. Im worried about the horses well being right now. I do think if you find an attorney, you have more than enough evidence proving your side. Hopefully you can get the horse back in the right hands. Good luck, people have given great advice. Let us know what happens