I think all people that sell birds have had experiences like what you describe. Those that care do what they can to prevent its occurance. I know how I feel when I lose chicks and definitely don't want a child, or any age, to feel the same way.I learned that lesson the hard way! I had a woman excited about buying seramas. Her kids already had bantams, so I sold them both of my chicks the next day after hatching. I saw the chicks eat & drink, and figured all was good. They put the car's seat-heater on to keep chicks warm on the drive home. The chicks settled into new brooder. That night the kids had a school function and when they came home one was dead. The second died sometime in the night.
Now I wait at least a week before selling any chicks. One reason is because they are more fragile - like quail. The second reason is I'd rather have a chick die in my possession than after a kid falls in love.