Local datasets are not accessible from a Workflow's destroy method. It looks like they are deleted right before the destroy method is called.
It seems like they should be deleted afterwards. A Workflow may want to read from a local dataset and perform some final logic in the destroy method. For example, it may want to emit a metric for the number of partitions added to the local dataset, or perform some aggregations on a local dataset and write those aggregates to a permanent dataset.