Tragically, this is what happens to most chams like flapnecks, Senegals, gracefuls. They get trapped by the hundreds in the wild, spend who knows how long at exporter facilities in crowded, too hot, too dry conditions, they get shipped halfway around the globe, sit in a wholesaler's facility again in crowded conditions with no individual care, and end up at a shop that has no clue how to care for them and can't tell the buyer much either. They didn't spend much to buy them so the loss to the shop is low. Chams hide their problems until they are simply too weak to keep up the show. They look very attractive when they are really stressed. His problems started long before you saw him. Even if your vet's office had done their job correctly he was in serious trouble. You need to make sure your vet knows how the office screwed up, and that this was a critical situation. If they couldn't see your pet they should have had a backup to refer you to.
The sad lessons you got to learn include:
Don't buy a wc cham unless you've kept that species before and know how what potential problems they will have. You don't want to contribute to the misery of imported chams and certainly didn't intend on adding to this one's problems.
Don't buy from a pet shop that can't prove they have a clue how to care for the animal. Check up on the info they give you...don't just accept it. Petshops that buy "cheaper" imports typically give out the wrong information, but the buyer who loses the pet later seldom ever tells the shop. DON'T RESCUE unless you know what you are doing and can convince the shop to change their policies on imports or what they sell.
Get set up with a herp-experienced vet BEFORE you need them and have a baseline exam done before problems show up. If only to get an established relationship going...the office is less likely to "lose" you and your pet in the shuffle if they know you. Also, if your vet hasn't seen this type of animal before it gives them a reason to educate themselves ahead of time. Then you will both know if another vet will be needed in an emergency. Have a backup vet for emergencies. Don't assume a vet can deal with a cham...most have never seen one.
Educate yourself about the species before you decide to buy it. Your house and climate may not be right for some species and it will be very hard to create a setup that works. With imported wc chams you don't have time to experiment. The cham is very stressed, dehydrated, possibly sick, scared, suffering from infections, parasites, and organ failure, so you need to be ready for anything right off.
I don't mean to sound harsh, but this is such a common story it just makes me sick. You didn't intend on causing any harm to your cham I know, but learn, take action with the shop, the vet, and hopefully any chams you decide to keep in future will do much better.
If you lose a cham FIND OUT WHY, so you don't unintentionally have the same problem again.
PS: I don't think the little pimples on the cham had much if anything to do with it's death unless there was an undiagnosed infection going on. They could have been subcutaneous parasites, but without a necropsy there's no way to know.