Nancy Drew is an incredibly popular series. I don't find it terribly surprising. Especially when I go to EBGames or GameStop you often find copies of the more recent Nancy Drew games whereas other PC Adventures are often lacking (although I've seen some).
I just went to EB Games on the 20th to see if they had the new Agatha Christie. The clerk looked it up and saw it was supposed to be released on the 21st and said I should preorder but when he tried entering it in the computer - it was too late to do that. He told me with 'obscure' games like that, I need to preorder as soon as I hear of the game to make sure it gets shipped to them.
I have other avenues to get the game, I just thought I would see if it was there.