Well he was just checking! Nothing would be stupider than for Hayner to leave school forever, and for Seifer to realize that he had NO way of contacting him.
He wasn't expecting the kiss... but it wasn't one of those offensive ones... and almost kind of comforting, so he let it go.
Hayner stuffed a few more things in his bad and then shouldered it, looking over at Seifer. "Well, goodbye, then."