I'm so sorry you have this idea that you know more about what happened here than what is contained in the article. where you in the store when the incident occurred?
You are reading more into the information provided and thus making judgement calls upon your own interpretation of said information.
You stated, more than once, your mother left you and your siblings while she went INTO ANOTHER ROOM.....major difference than this instance where there was only about 5 feet from mother and child.
You don't know if this child "wandered off" - he may very well have been placed there by mom to wait a few minutes, just like your mom did with you and your siblings. And his playing may have been nothing more than making faces in a mirror - children enjoy that.
You don't know any of these things, do you? Yet you will condemn this woman - your attitude tells me much about you.
Again, the childs safety is the responsibility of the parent.