That puppy isn't worth $42k, trained or not.
Most fully trained service dogs top off to about $10,000 ($2,000 for pup, $2,000 for training, $6,000 for food, treats, traveling, time, vetting for 2 years).
He is taking advantage of you.
If the puppy is not able to recover and do training, then it wasn't service dog material anyways. That is why many get washed out-- because they cannot overcome a little minor negative experience (poor nerves, low threshold).
If he didn't offer his exchange of contact then I wouldn't have given him mine.. Any reasonable person would want to sort this out under the table. I think he is just trying to scare you.