I'm going to be right out front and open here:
1) The so-called Pet Store that sold you these two should likely be investigated at a minimum. Terrible condition of animals, poor advice (I know, that problem is pet-store establishment-wide), and bottom-line pushed poor animals to death. That should NOT be allowed, PERIOD (yes, and I apologize for my language now, I am rather pissed off that a store is willing to stoop that low to make a buck)
2) When I get an animal, whether from a store, breeder, individual, or animal resource center; I am not just getting an animal, I am welcoming a new member of my family home. They aren't just 'throw-aways' or simple pets. So in a way, I am a bit agitated in just 'taking it back' after it did start to show some progress toward recovery. I understand, after your rebuttal/enlightened post, that you did seek professional opinions on the health of your baby beardie; and am therefore a bit less agitated. What stirs me most though, is that the little one was sent back to certain death in hands of cold and callous individuals versus given the chance to live (or die with someone who cared for them).
Maybe it's just me, but I have a real attachment to my little ones (be they my Beardies or Cats). Perhaps hearing why I am that way may shed a bit of light:
When I got Cooper, she was tiny; much smaller than her cage mates at the pet store. She was purchased with 3 others when my now-ex and I knew nothing about these beautiful creatures, and by my ex. As I was setting up a home (properly) for her, she stayed at my now-exes place (with her cage-mates). I get a phone call 3 days later, from the Ex, saying my little girl had been viciously attacked by the largest in the terrarium and her head had been split wide open/neck bent to one side. The picture she sent told of my babies imminent and impending death. I took off work and went to get her (we lived in separate places due to her in school). When I got there, she really was as bad as the pictures showed. I bundled her up and brought her back to my place, preparing to bury her within a few days. I took her to the vet, and the vet gave her no chance of survival. I brought her home to die, or to live. I did everything I could think of to save her, and some things that probably shouldn't have been done. She recovered, but never grew any much more physically larger than her 10-week size. She lived two years, but those were the two best and most loving years I had with any Dragon (that includes the ones she was purchased with, and after I got Smaug from his 4th or so home (Smaug was great too, but Cooper was more loving)). I didn't give up on her when she should have died. These little critters are terribly hearty.
All I am really saying is: Now you will never know if that little one would have made it and been one of the best investments in a family member you ever made.