Going Home - S3-E11
Other mistake: In the October 2011 flashback, when Mary Margaret gives Henry the storybook for the first time, he opens it to show Pinocchio and Geppetto in an illustration. However, according to 1-20 "The Stranger", Pinocchio's story was not added to the storybook until later after August came to Storybrooke, several months later. This is confirmed in 4-13 "Unforgiven", where Regina and Henry look at the exact same picture, and notice that the paper is different than the rest of the book, because this particular story was added by August. (00:17:00)
Going Home - S3-E11
Revealing mistake: In the convent, when the Shadow knocks Hook off his feet, sending him sprawling onto the ground, the one who actually falls down is Colin O'Donoghue's stunt double. (00:11:10)
Going Home - S3-E11
Continuity mistake: When Peter Pan removes the enchanted black leather cuff from his arm, he uses his magic to transfer it to Mr. Gold's wrist. However, as he sends Mr. Gold flying across the room, there is a close-up of Pan's arm, where the cuff is back on his arm, next to the normal brown cuff that he usually wears. (00:21:20)
Going Home - S3-E11
Continuity mistake: In the Neverland flashback, when Hook offers Tinker Bell the rum bottle, the stopper (attached to the bottle) is hanging over the back of his hand. In the next shot, it is not. (00:09:55)
Answer: He knows who she is because he knows that the fairy tales are true. He was also shown to sneak out to go see Emma or someone else. Sometimes he succeeded, sometimes he didn't. This is how he knew to look for her despite his strict mother.