A worker told police she found the bag on top of a box outside around 5:30 p.m. Wednesday. She brought it inside.
Employees told police they heard nothing before locking up and leaving for the night.
Police have said whoever left the child is likely to face charges of child cruelty by neglect.
Georgia has a “safe haven” law that allows a legal way to abandon newborns within seven days, but the mother has to give her name and other information and leave the child with health care workers, face-to-face.