I completely understand where you are coming from, however.
For me, as someone who has struggled financially and had some rat bag horses along the way, I would have loved the opportunity to ride a well trained horse, and have a been there done that to take to a show.
Naturally there are risks.. but there always are with horses. If the horse will find that one sharp thing in acres of field, it will ;)
Agree with Saddlebag, however. Did you get it in writing?
Another thing I would have insisted on is a written contract, as I did with leases on my old horse, and what I have drafted up for a horse I now have on lease. Who is responsible for care of tack, if the horse is injured in a lesson, or as a direct fault of the trainer/rider etc who forks out for vets bills?
Sorry to go off subject, but I really did learn the hard way, that when it comes down to the nitty gritty of money no one is your friend.. especially in the horse world!