A: The only reason that it says “if the card is not in play” is that your very FIRST option is to just take it from in play in front of any other player: the first words are simply “Put the Necronomicon in front of you.”
Only then, “if the card is NOT in play” i.e. obvious on the table (emphasis added), THEN you can go looking for it in various places, first in other players’ hands, then the discard pile, then the draw pile.
The Grand Theft Biblio card is supposed to almost always simply give the person playing it the Necronomicon. The only things that would prevent this would be if someone countered the Action with the Surprise The Stars Are Wrong, OR, if the Necronomicon was in the only place not mentioned as searchable: face down in front of a player waiting to be played due to Dreams & Omens (See If the Necronomicon has been distributed by Dreams & Omens…
I suppose it would be clearer to start with “Take the Necronomicon from wherever it is on the table, and put it in front of you,” and then go on to your options if it’s not in play, but it gets hard to fit all the important information onto cards sometimes.