User blog comment:Miskos3/Fairy Tail 529: Teacher, Review/@comment-7418318-20170401075358/@comment-1359322-20170401102326

Well according to Zeref he couldn't control Natsu as a child, so he send him to Igneel. Igneel probably tried and fail too so Igneel sent Natsu to Anna, the scarf was most likely sewed in that interval.