RE: Any experience with bHCG injections to enhance descension?
Even if you did administer the injections and it was successful, this dog could still be at higher risk to produce cryprotprchid.
I am aware of several cases of testicles dropping up to 4 months of age but it is rare.
A pup should never be sold without a health check-up and testicles being checked by a licensed Vet and documentation of it being done.
If one or both testicles are not down by the time the pup is sold, the Buyer should be aware of this prior to purchase and allowed to get their deposit back or move their deposit to another litter. Anything short of this is unethical. Either the breeder is incompetent or a flat out lie, and you, the Buyer should not have had this put on you without your prior knowledge and agreement.
If your contract or even emails sent to you from the breeder stated that your puppy you were paying for was show/breed quality and you were shipped a cryptorchid puppy, that is false advertisement and the Breeder should be held accountable for all cost incurred for you gas, time, shipping, shots, food, vet check-ups, and possibly even emotional stress (getting attached to pup then having to let let it go).
It is not the cryprotprchid that is such a huge issue (which is a minor health issue compared to the many other non-fixable health issues), it is the fact that you were not notified of this ahead of time in order to allow you to move your deposit to another pup that was breed/show quality. Even if you were purchasing a pet to be neutered, you should still be notified ahead of time and allowed to discuss other options or lower price.
If the breeder said it was down when they shipped it, then ask for the Vet record to proved this. Otherwise it is just hear-say. And even if it did suck back up why is that your fault and you be stuck with holding on to a pup for months to see if it goes back down.