Kids Will Be Kids
Kids can have an unhealthy obsession with anything. It could be a toy, a rock they found on the ground, or something much more disgusting. This nanny had caught sight of the kid they were watching fast asleep in its crib, but there was a mysterious black object right next to them.
The OP ran into the nursery to see what was actually going on. That’s when they learned that the kid had an unhealthy obsession with garbage bags and was sleeping comfortably inside it. The nanny didn’t elaborate whether there was garbage already in the bag, but we like to assume the worst.