As every other ItemsControl, ScatterView creates and manages its item containers by an ItemContainerGenerator, which provides methods to get the container for a certain item or to get the item for a certain container:
ScatterView scatterView = ...
object item = ...
ScatterViewItem scatterViewItem =
scatterView.ItemContainerGenerator.ContainerFromItem(item) as ScatterViewItem;
or
ScatterViewItem scatterViewItem = ...
object item = scatterView.ItemContainerGenerator.ItemFromContainer(scatterViewItem);