Ugh! That would kill me! I don't know that I'd turn down the petstores offer though because there's a little tortoise in line that may just need someone like you to give it extra special attention asap. Plus, maybe, you can teach the pet store how to identify this issue and maybe relay the message to the breeder.
So sorry to hear about your little tort, what an awful experience for you but you did your best and at least he isn't suffering anymore. I just hope you find another little tort to give a good home to soon.