The voice was Karyn's dad!
Karyn thought quickly, and said "Sorry Dad, I'm OK - I just slipped and fell, but I'm fine."
Karyn's dad said "Why is there a huge crack in the bathroom door, sweetie?"
Karyn looked at the door and thought "Oh shit!" She still had the stone in her hand, and whispered "I wish there wasn't a crack in the bathroom door."
There was a flash of light, and the door vanished. Karyn's dad was standing, shirtless and half dressed, facing the empty doorway. He was staring at his daughter, completely naked, straddling a teenage boy, obviously in the middle of having sex.
His face grew red, his eyebrows furrowed, and he opened his mouth to start yelling. Quickly, Karyn said "I wish Dad was at work already, and that he forgets about catching us!"
Karyn's dad vanished with a flash of light. He had a hard time explaining to his boss why he showed up at work without a shirt or shoes that morning, especially as he couldn't quite figure it out himself.
Meanwhile, Karyn pulled her self off of Jon, grabbed a towel to cover herself, threw another at Jon, and dragged him to her room so they could get dressed.