For a moment I thoke Emma is Maleficent's daughter and Snow and Charming (who had Lily, a future villain) for have a future hero They changed the children. But after I remember the scene in the season 1 when Snow gave birth Emma
You know, this thought crossed my mind, as well. Their use of the word "lost" was a vague choice. And as written above, I also wondered for a moment if there was a "switched at birth" incident. But I'm guessing Maleficent just gave up her baby to escape the curse.