When the light was gone, Sarah looked down at herself in shock. She was a little girl... "Ugh, I'm a kid!" Sarah yelled out in disgust. It was weird for her to hear a high-pitched little girl's voice instead of her own.
Mikey, who had turned into a buff teenager...the male equivalent of Sarah, stood up. Since Sarah was whispering her wish to herself, Mikey didn't hear it and didn't remember the previous reality. Mikey looked at Sarah, clearly annoyed. "Why'd you bump into me, kid?! Get out of my way!" he yelled and walked past.
This was a case when Jon's "precautionary" wish came in handy. Even though he wasn't in hearing range of Sarah's unfortunate wish, his memories didn't get altered and he still remembered how things were supposed to be.
