You saw a kid with their mask on. You talked to them about enjoying the festival. They agreed with you, then Carmine noticed the kid, and you ran by the stairs to see the new kid. Carmine shouted to the kid, and they flee up the stairs before dropping their mask on the ground. They ran away after you picked up the mask. The info of the mask says that Ogerpon dropped it after fleeing up the stairs, and you, Carmine, and Kieran went back to the Community Center.