From the piece:
"Two-year-old Ryan Gildow remained hospitalized Monday night following surgery. He was listed in fair condition after the bullet was removed."
As has been mentioned, this was a .380 and not known for it's overwhelming power, and it was fired at the ground (concrete floor?) to boot. For it to still be lodged in a two-year-old's leg means the round was nearly spent or (most likely) only a fragment hit the child. Very fortunate indeed.
I'll add my prayers for the little boy, the parents, the owner of the shop and yes, even the idiot who screwed up. As said by Levy78, perhaps this story will cause someone to check the chamber before they handle a firearm when they may not have done so otherwise. Some good may come of it and we will never know.