As a child, she was skipping through a park. Ino and her friends had already picked on her and she was doing her best to forget. So on she skips, until a van rolls up alongside her. "Hello little girl", said the driver "Would you like some candy?"
"Of course" said Sakura. For who doesn't love candy. So Sakura gets her candy and gets in the van. The van drives for many miles, finally reaching its destination.
Sakura and Kabuto get out of the van and enter Orochimaru's lair. Here he injects her with a new serum he had been working on. That serum suppressed her natural abilities, making her useless. She was then returned to her bed never knowing why her power and usefulness were essentially gone. The serum had one side effect however- it implanted Oro's love for Sasuke into Sakura.
Kishi would use this as a lesson to teach children to always accept candy from strangers. It would be rude not to