I don't know anything about this story, but I do know without a doubt that toddlers do indeed open doors and run out of houses by themselves.
We had moved into a brand new subdivision with plenty of empty lots and houses under construction. I had an infant and I sat down to nurse her while my 2 y/o son napped (or so I thought). The builder had installed a latch deadbolt and apparently my wily little guy knew exactly what to do. My new neighbor caught him running down the street stark naked (yes he was one to shed his clothes as well) and I hadn't even realized he was gone! To this day I shudder to think of it. We had all sorts of construction debris around, not to mention construction workers!
I hadn't heard the house alarm beep when the door opened. My husband changed the locks to a keyed deadbolt that very evening!
But for the Grace of God!!!
Toddler's ability to open locks (which we all know they can do) notwithstanding, what I find very odd is that no one has reported seeing or finding these children. This brings two scenarios to mind, they have been abducted or something in that household is fishy and things are not as they have been reported.