Poor Cassy

Jacob woke up to the sounds of baby Cassy crying her eyes out, he woke up to see the infant wiggling and trying to move with clear distress. Jacob slowly got up and yawned, Cassy stopped crying in an instant, she was watching him carefully. Jacob could see the panic in her eyes, the worry that after all she had done to him yesterday, today would be his chance at revenge.
"Morning Cassy," Jacob said cheerfully, the baby glubbed in an attempt to speak, confirming the fact that Cassy although looking like a innocent baby still had her adult mind but lacked the equipment to utilize her voice.
"Okay so I think you need to learn a lesson," Jacob started touching Cassy, "I'm going to make you older so you can talk but it's your turn to be punished. You are five years old."
Cassy grew up in front of him, going from a tiny baby to a very grumpy little child, she covered herself up with the duvet and crossed her arms in a typical child-like manner. Jacob laughed, she was really rather cute for a toddler, he had never seen any pictures of her at this age, she looked like her niece.
"Change me bwack!" she demanded grumpily and suddenly.
"Oh no I won't," he laughed, "Not until you've learned your lesson Cass."
"I'm sowwy," she pleaded, "Make me older, pwease?"
"Not yet, now you better behave yourself or you'll be spending the rest of the day in diapers!" Jacob laughed getting up, "I'll go make you some breakfast, don't bother looking for the necklace, I've hidden it..."
Jacob left the room, Casey pulled over one of his large shirts and threw it on herself, it was like a nightie on her. As Jacob hummed to himself in the kitchen, she took against his advice and began searching for the necklace, of the things she'd do to him when she got that back in her possession.
Her search was interrupted however when the phone on her side table began to vibrate, she moved to it and saw that Jacob was getting a call from her phone, she picked it up and put it to her ear, "Hewwo?"
"Hello, is Jacob there please?" came the voice on the other side, "It's important."
"Is this the girl wiff the pwanties?"
"Yes, who's this?"
"Our addwess is 123 Fake Stweet, here's the pwost code," said Cassy sweetly, "Come over if you want you boyfwend back to normal."
Then she hung up and carried on her search, finding nothing, where on Earth had Jacob hidden that necklace?