I don't think the author was implying that stopping when the note is found implies a "lucky" personality. I think Dr. Wiseman was looking for personality traits that are common amongst "unlucky" people. The newspaper test demonstrated that unlucky people are more tense and anxious than normal, and this could explain why they may not spot new opportunities.
I agree. But does this actually follow the definition of lucky? A person could deem herself lucky without that actually being the case-- it might just be that she has personality traits that make her successful. Luck, by definition is not dependent of one's actions. I guess the article is saying that we can make ourselves feel lucky by working on certain personality traits-- but does that make us actually lucky? I am just being philosophical here.