Find out how Lori disappeared by checking out the table in the dining car when you are in Copper Gorge and the Hardy Boys have left the train. You can't do this before you arrive at the destination or when someone is in the room. You have to do it before you get Charleena's autograph and give it to Fatima.
You can look at the table near where Lori was standing when she disappeared and you'll see a button that looks like the carpet and if you press on it, you'll turn around to the bookshelf and see that the shelves open and Nancy will comment on it with either : 'This must be how Lori disappeared' or 'So, Lori pushed that button, slid the shelves open further, squeezed through, and disappeared. Very clever.' You don't have to do this but it's kind of interesting.