It seems fairly plausible that the child caused something to need cleaning and quickly ran off while the mother was distracted trying to find a towel while picking up ice cubes or something. Toddlers are a lot quicker than they should be for uncoordinated, disproportionately headed accidental suicide generators
Also it could be a cultural norm. Not every culture micromanages children. Hell in some countries its normal to park the stroller outside a cafe ect and leave babies outside while parents eat inside. Im not saying it's safe or the best option for every kid, but it's also not entirely black or white.
Lorenzo: Not if I bite you first