And Straight on Till Morning - S2-E22
Continuity mistake: At the beginning of the scene where Baelfire confronts Hook about Milah, when Hook is talking to Smee, the hair on his forehead keeps changing between consecutive shots. (00:25:55)
And Straight on Till Morning - S2-E22
Continuity mistake: In the scene where Mr. Smee asks Hook why Baelfire is still aboard The Jolly Roger, when Hook says "Anyone who disobeys can walk the plank and pray the mermaids take pity on his soul", as he begins to walk down the steps, Smee is several meters away from that area, with his back turned (look behind the mast). In the next shot, he is much closer to the steps, and is facing the viewer. (00:26:20)
And Straight on Till Morning - S2-E22
Continuity mistake: When Baelfire attacks Hook, as Mr. Smee is heard saying "captain", Smee runs a few steps, before putting his hands on the railing. In the next shot, he comes running again, and once again puts his hands on the railing. (00:26:25)
And Straight on Till Morning - S2-E22
Continuity mistake: When Baelfire is getting ready to leave The Jolly Roger, his right hand, which is holding onto the sack he carries behind his back, keeps moving up/down between shots. (00:29:15)
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.