At a young age Izuku and Katsuki were taken from the park and were labelled missing. Not too long after they went missing there was a couple pro hero search teams sent out to find them but none of them found anything. As for Izuku and Katsuki, they had no idea where they were and no idea what they had coming. Also Izuku and Katsuki still call each other by their nicknames ( Deku and Kacchan)