OP--my first thought is that you use such over dramatic language (parents "abandoning" their kids, etc) that I tend to feel you are likely over dramatizing the whole situation---meaning the parent who left a child to browse the toy aisle was likely gone 3 or 4 minutes not 30, etc. I also note that only one of the three incidents took place in the store where you are an employee--yet you act as if you working somewhere in the mall at all gives you some sort of extra authority, or makes you a safer adult, etc. Which I find odd.
As a parent who gave my kids a lot of freedom, and never taught them to be ware of strangers, but rather taught them what was and was not appropriate behaviour from others, especially other adults, here is how I would read each of the situations you describe:
1. Playing on the escalator. Yeah, that is not OK both because it is rude to others who need to use it and it is dangerous. Kids playing on these is actually one of my pet peeves. That said, unless the child actually had a stuck shoe or lace, etc I would not intervene directly and it is (sadly) so commonplace I cannot imagine bringing it up later on a message board as if it were some unheard of thing. IF it were ongoing for more than a minute or two and did not look like it was going to stop, I could see where you, OP, as an employee at a store in the mall, but not mall security itself, etc might report it to mall security to let them handle. Or, if I were really worried about the child's safety, I might stand near the emergency stop button and keep an eye out until the child moved on (I have done that a couple of times--especially when a child with longer hair was laying on the steps as an escalator went up).
2. Child left in the toy aisle of a store laid out such that it is "big enough for kids to not find their parents but adults can see over all the racks": well, that indicates that the mom could almost certainly see her child while she was shopping and was probably looking over every minute or two. It's likely the child who approached you had only just become concerned and teary eyed and mom had not seen it yet between glances, or simply had not had enough time to get there. Rather than engage the child in conversation a moment and ask what the mother was wearing so that you, yourself, could look over the racks and find the mother without the child leaving where they were told to wait--you told the child to head up to the front of the store? Seems out of line to me---and it seems pretty obvious that the mother was in fact paying attention given that she made it to the front of the store to get her kid faster than you did trying to keep up with the child you had directed there.
3. A parent leaves a child sitting at a table in the same food court the parent is in to get food. Parent can, at any time, glance over and see the child, Child is happily looking at a purchase and in no distress at all. You choose to strike up a conversation with the young child with the parent not there? Yeah, that is wrong and the type of behaviour my kids were taught to see as dangerous. Not because you were a stranger, but because adults do not randomly start conversations with unaccompanied children.
