Another Vanishing Act

Jon looked around for Karyn again. What he really wanted to do was discuss the situation privately with her, if indeed Sarah had described the situation accurately. And then something happened. All the girls (Sarah, Melissa, Tiffany, Zoe - *all* of them) disappeared. And at the same time, everyone who had previously vanished (guys, adults, kids) reappeared again. Jon was relieved to have them back. But what about all the teenage girls? Where did they go? And would they ever come back?