There are certain nightmare scenarios, I think, that *every* parent and grandparent has - scenarios that keep them up nights. A missing child is one of them.
While most children do walk, learn, and play safely, it's fearful when even one does not. My heart goes out to the family, friends, and classmates, whom I don't know but who are just a couple of hours away from us.
Even when I was a child (which was *quite* a while ago!) these things happened, and I remember being warned of the same things mamas are warning their children about today:
Don't talk to strangers, however "nice" they may seem.
Don't accept candy or anything else from strangers.
Don't go with strangers when they say, "Want to see something exciting? Come here!"
Don't go with (or to) strangers when they say, "Can you help me?" or "Your mother sent me to pick you up," or "It's okay - I know your brother."
Do not get into strangers' cars.
"Stranger" means any person *you* do not recognize or aren't sure of, whether the person says he/she knows your family or not. If it turns out to be your dad's boss or your best friend's grandma, you've still done the right thing.
Stick with your parents when you're in a store.
Buddy up when you walk to school and play at the park.
Learn to be a noticing person, and take note of anyone you think isn't part of your neighborhood or is doing something strange, so you can tell your parents or teachers about it; the person may be okay, but it's worth mentioning.
Learn to be assertive, even to big people. Assertive means standing up for yourself and your friends. If it's hard for you, ask your parents to let you learn somewhere. It's not always rude to say no to a grownup.
Even if you know who the person is, it's all right to say no, and even to run away (to your home or your school)!
Know your neighbors - both grownups and kids - and be on speaking terms with them. (A corollary to this might be, for parents: if your neighbor works nights and feels she can't take her child to school, no matter what you think of it, step up and be the one to say, "She'll walk with us. We'll come for her.")
All those lessons are wise ones and have been taught for generations.
I don't remember being taught to scream if somebody grabbed me or if I saw someone else being grabbed, but I sure think it's a fine thing to learn. It ought to be great for kids to know that, for all they're told not to make so much noise, there's at least one *wonderful* opportunity to yell your head off.
Villainy comes in many forms and is very clever. Parents can't protect their children from everything that might happen, but they can try their best.