Thankfully or maybe not, chickens don't share our human sense of loss, but any time you separate a chick from its brood and then reintroduce it or add a different peep you run the risk of rejection.
It usually works best if you add a smaller peep into a clutch of older or larger peeps. There is less chance of the hen rejecting the younger smaller chick as she views it as less of a threat to her own brood. This is also why I don't like natural hatches that drag on for days and days.
By the same token a hen with two dozen chicks is no prouder of her clutch than the hen with only one chick, and the hen with 24 peeps will still be just as happy with only one chick as she originally was with the whole 2 dozen. In other words being a chicken is emotionally easy.