I wouldn't consider the situation that dire of a problem unless it was happening repeatedly. In this case I am sure Baby's mom will be more careful in the future. There is certainly not much of anything that can be done after the fact. Just have to be more careful about where Baby is when she is unsupervised.

When Tasha was 7 months old one time, I needed to run an errand and she was sleeping peacefully. She was house trained by then and had been left for short periods of time before without problem so I went ahead.. got back and she had chewed a little hole in the sofa cushion and was gleefully pulling the stuffing out of it. I think I felt a mixture of horror and hilarity. But, I learned from it and was much more careful about leaving her unattended and running the house until she matured a bit more.