Normally, NetNewsWire deletes news items when they disappear from the feed they appeared in.
You can change this behavior: you can tell NetNewsWire to keep items longer.
You can over-ride the setting in the preferences window for groups and for individual subscriptions.
The settings for a group apply to the subscriptions inside the groupÑand you can also set settings for subscriptions inside a group that has custom persistence settings.
Another way to keep news items is by flagging themÑsee Flagged Items for more information.