Hi Tamara,
Baby reptiles are not as hardy as adults. It's always best to buy an older juvi or sub-adult unless you get some kind of guarantee. You didn't mention if they were shipped? I assume they were because your emailing them and not seeing them in person. Was it an individual, breeder or petshop?
If they were shipped, they went a day without food and water, may have been exposed to extreme temps if weather wasn't considered when shipped. How big are they and how old did he say they were? When receiving a reptile that's shipped, it's best to give them a warm soak, and get them set up in a private enclosure where they can get the right temperatures and humidity conditions if necesary. Leave them alone to let them get aclimated to their new home. Sometimes it takes them up to a week to start eating right, but in the case of a tiny baby, they can't go that long without getting dehydrated. It's hard to offer advice on special care when you don't see the lizard. I don't remember your saying how his weight looked. Does he have a full tailbase or are his hipbones protruding. Is the tail full underneath. That might tell you how long it's been sick for. He could have came down with a uri from the trip.
You'll have to make the choice of bringing him to the vet where it would be pricey, or hold onto him, keeping him warm and hydrated with daily misting, not handling unless a necessity. Join a monitor list at yahoo.com if you need help with care. You can also take steps to get a refund if it's due.
If you bought from a petshop or breeder with a website, check their refund policy. Even if they say no returns on their site or a receipt, they should still respond to your request for help.
I would email them once more, notifying them that if they don't respond, within 2 days, that your going to post your experience as their customer, to the BOI on this site. If your not familier with it, go to it and learn the rules.
Good luck!