Puppy ate a piece of plastic bag

Two days ago, I was picking up my puppy’s poo in a plastic nappy bag when she grabbed onto it with her teeth. Long story short, she swallowed some of the bag (about a 1cm by 0.5cm piece). I know this sounds like a small amount but she is a very small dog. She is a 14 week old chihuahua puppy and weighs only about 600g.

I called the vet straight after this happened but they just told me to watch her for signs of vomiting, trouble pooping etc and it would probably come out in her poo within 24 hours. Well, it’s been over 48 hours now and although I have been thoroughly checking all her poos it has not come out yet. Called the vet again and they said to keep watching her as she is showing no symptoms of an obstruction.

How long might it take to come out? What if it never does? Does anyone have a similar story with a happy ending to make me feel better? I’m so worried!