The idea that it even matters that there is only one Lucy is based on a huge assumption. The fact is, most animals, the vast majority, never leave a fossil behind. It’s estimated that far less than 1% of the animals that ever lived leave fossils. It requires a nearly perfect mix of anoxic environment, compression, and minimal disturbance for thousands of years. We wouldn’t *expect* there to be a fossil to represent every kind of organism that ever lived.