Drug that makes a concious person go blank in a second

I heard a lot of stories from my homeland recently that some people are "casted with dark magic" (or whatever they call it) while talking to strange people. The stories all seem similar, victim is walking/waiting/doing her own stuff (they usually target ladies), while a completely stranger approach her and ask her something, maybe asking for direction. And  when a victim answers and gets involved in the conversation, suddenly the victim's mind goes blank, she can't remember what happens after that, only wake up to realize she was stolen something

So people call it "dark magic" but I believe it must be some kind of drug being used here! I'm quite curious and hope to find an answer! I don't believe it dark magic or anything. The victims might had inhale a non-smell drug that stop their brain from working temporarily. In some cases, victims reported that they couldn't think of anything and they did whatever the stranger asked them to do! 

What do you guys think?