Upsetting afternoon

My DS(8) was outside playing with his friends. The doorbell rings, and there are two teen girls on my porch selling magazines. I had no idea who they were, but they said that my son (and they named him!) sent them over, and had this whole sales pitch on how he thought I was the best mom ever, etc... I obviously wasn't thinking straight, because it had me totally off guard, but after they left, all I could think was "Why were they talking to my son?!?!" Shouldn't that be one of the #1 rules for them ~ not to talk to children?! And what about my DS?!?! How many times have I told him NOT to talk to strangers?!?! Well ~ to make a long story short, my DH and I had a LONG talk with my son. We explained that strangers don't only look mean or old ~ a stranger can come in any shape or size or age, etc... We told him we didn't know who these girls were, and by their accent, they definately weren't from around town! It really had my DH and I upset, especially since there was a child abductor walking around our town not too long ago (he was caught, thank goodness!), and we had just talked to our son about strangers at that time! I just wondered what you all would have done in a situation like this? I obviously wasn't thinking quick enough, or I would have probably told the girls they really shouldn't be approaching children. I just wish we could feel safe in our own neighborhoods, and that our kids had the freedom to play outside the way we used to! Thanks for listening!