By the same logic, driving your car while drunk is not a problem as long as nothing happens. Right? But, that's not the point. The point is you shouldn't drink and drive because it increases the risk of something happening.

While I agree that carrying an egg timer is not a crime, I still think it is foolish to fly without knowing what's in your luggage, especially these days. The point being that if you don't know what's in your luggage how can you possibly be sure it's all harmless? I think the girl rose suspicion not because she had an egg timer but because she was clueless about it, spurring the question: what else was she carrying without knowing about it?