When you delete content in QSToolbox, it's marked as 'deleted' but not gone forever. You can restore or undelete content. 

You will need to be in the 'Staff' user group or the relevant module_manager group to be able to undelete items.

In the relevant module, look for a link [Deleted] on the right at the top of your search results. (If you can't see this link, then you don't have permission to undelete items)

This will list all of the deleted items in this module. Click on the one you want to undelete, and then look for the "UNDELETE" button at the top right of the view:

Click UNDELETE and the item will be restored. 

When you delete a top level item, like an Asset, Contact, Employee etc all of the content it contains, like tasks, comments, etc are also deleted. When you UNDELETE a top level item, everything it contains will be restored, including any items you may have previously deleted individually.

Undelete Tasks, Comments, Records

If you've deleted contained content like tasks, comments, records you can still restore individual items but the interface is a bit different. Look for a "Show deleted" link at the top of the listed items. When you click the link, the deleted items will be revealed and highlighted in the list:

Click on the undelete icon to the right to restore it, or open up the item and use the Undelete button as shown above.