If I remember right the Debenhams wasn't a straight forward assault in a toilets- the kid was grabbed and marched through a crowded high street and then taken to the toilets in Debenhams.
I agree with the other advice here, and agree that although it is good to be aware it shouldn't be something to worry yourself about too much as it does seem rare. And giving advice to your son if somebody does approach him is good!
"...until lambs become lions"
I love you, little lewis, and i will never leave you. We are the same. You brighten my day, and i will make sure that i brighten yours. Hugs and kisses.