No need to worry.it ll pass down and come in stool.if ur baby showing vomiting,stomach pain,not eating properly,then u consult me further

Can help you with the next course of action and treatment plan. Would like to discuss in details and provide apt solution. Kindly consult.

if the child complaints of pain abdomen or shows symptoms of bowel obstruction rush to the hospital.

9 months old baby can pass stools of the thickness of 1cm × 1cm. If that be so then this plastic piece of 1 × 1cm size will also pass with the stools. The only thing is that it shouldn't have sharp spikes or edges. The other answer is endoscopy and taking out the plastic piece. This piece can't be seen by X ray or Ultrasound or CT . It can be seen only by MRI. Even if it is seen it is going to be a major procedure under Anaesthesia to remove it. I think it is not worth the effort. So wait till the piece comes out with stools.

Visit nearby pediatrician for physical examination