a mamin, you were a little harsh in your response, IMO. Yichusdik did not sound accusatory as you imply. What Yichusdik said is correct in every way. Although you are correct that Hashem is in charge, we have to put our own efforts into our lives and safety.
If you jump off a building, Hashem probably will allow you to break your neck. If a young child is allowed to walk home from camp, it may or may not be a good idea and he may or may not get into difficulty. In this case it unfortunately had a tragic ending. It could have easily gone the other way, too, where he would have safely found his way and met up with his mother. We cannot comprehend why this terrible tragedy occurred, but there is no question that as parents we are obliged to talk to our kids and spell out b’feirush that there are vildeh chayehs out there, sometimes wolves in sheep’s clothing (apologies to Wolfish Musings)who appear kind and nice, but are still dangerous.
While we don’t want to turn our kids into terrified little wusses, neither can we ignore the obvious. Sometimes monsters have pleasant faces. A stranger is someone you and your family do not know very well, and you don’t go ANYWHERE with ANYONE. Prayer is a good thing, but prayer alone will not teach our kids the skills they need to be street smart.