Destroyed/Decommisioned Resource Starbases

When I conquer an enemy completely his starbases disappear. If the starbase was built on a resource, the resource symbol still appears on the game map, but won't show up as a resource if you put the mouse pointer on it. Is this a bug? Does the resource tile get destroyed when the starbase does, yet still show on the map? If you rebuild on the resource, you don't seem to utilize it. Just wondering...