hair elastic
when a guy gets a hair elastic from a girl it means she's been checking him out and now she's got proof. And he's got a piece of her hair stuck to his face.
He got the elastic from his teacher's daughter and now he has to wear it during math class.
He got the elastic from the girl next door and now it's in his backpack like it's a secret.
He got the elastic from his crush and now it's on his forehead like it's a curse.