The previous batch got eaten by someone, maybe even by their own parents. The parents were doing a great job for the 3 days they let the fry go out once in a while, then the fry disappeared and the parents have returned to every day sand digging and eating.
This is why we have taken the batches we want as soon as they are out. Though, we can have any new ones at the moment, so it's only good that they are gone.