N.B.
All I can say is that dogs and children know when something's not right with a person. Don't blow it off and keep a watchful eye.
My 4 year old daughter loves EVERYONE and is very personable to strangers. When someone approaches her and she hides behind me, we exit immediately. I do not make her shake hands or speak to them if she is uneasy. I do not want her to ignore that "voice" in her warning her of danger.