We're guessing this sneak peek takes place immediately after the curse was cast, as Regina (Lana Parrilla) seems to be testing how well it worked.
First, she comes to Mary Margaret's (Ginnifer Goodwin) classroom, and asks how long she's been teaching there. "I'm not sure," Mary Margaret says, confused. "As long as I can remember."
Then she takes Mary Margaret to see David (Josh Dallas) in a coma, and asks if Mary Margaret knows who he is. When Mary Margaret says no, Regina explains that he's a John Doe. Mary Margaret, ever the optimist, says maybe he'll wake up, and someone who loves him will find him.
"I wouldn't count on it," Regina snarks. To be fair to her, as we all know, it does take a very long time before that happens.