Yes, it's really difficult.
I was talking to my 11 yr old daughter about it and how can they really understand. Mine want to know why anyone would want to take a little child and what for. Well how can you try to explain that.
Also the thing about it being someone possibly known by the child. We live in a tiny very close community and mine do see neighbours almost as family. They are older now and listen to news reports ... I can see their confusion.
I went through, as I always have, the yell, run and tell , with mine again last night. They asked about people they knew and I said that if someone they knew well asked them to go with them, then they come and ask us first and that if that person was genuine they wouldn't mind that at all. NEVER go without asking. Also told them that things like this are very rare.
Trouble is that you can never really tell how a young child will react when put in a situation. My daughter comes home on a school minibus and one day I got a call from a mother at the school to say she had taken my daughter back to her house, half an hour drive from here, to play with her child. It was not arranged and I am not close friends with the mum. It caused some chaos and distress - she wasn't on the bus, people assumed that I must have collected her, etc. My daughter is quite a mature, sensible girl and I was surprised that she had just gone like that.
She said she felt awkward saying no to the parent. You can imagine how our discussion of the event went.
Okay the parent had no ill intentions but it did show me how easily a child may go with someone they know (and not that well). She was 10 at the time and an intelligent girl ..... spoken to quite a lot about dangers etc.