If you go to the asset store and then click on the Deleted tab, you will see a list of your assets that have been deleted. Any asset in here can either be restored or purged (permanently deleted). To do this, click on the icon to the left of the asset title, and choose the I want to... button. Any deleted assets that have been shared will not be visible to those you have shared it with. If you restore a shared asset this will be reinstated. Assets that were in the deleted section that were manually chosen to be purged are no longer available.