Robot Chicken
Seriously?
Does it? Surely if this was her favourite teddy, she would want to take it with her and would be kicking and screaming to have it back. I can't imagine the 'kidnapper' would have a chance to place it calmly on the shelf if (s)he was intending to take the kid as quickly as possible? If you want to ensure that you can placate a child, then a teddy bear is a very good option.
Chloroform? Was this an opportunist kidnapping or was the perpetrator prepared? Some reports say Maddie was kidnapped to order.
The window of opportunity was 5 minutes. I don't think it would be possible to kill someone and clean up the mess within that time period.