To find archived object, follow the instructions in Display archived data.
To unarchive or restore an archived object, simply right click on the object and select "Unarchive".
Or expand the navigation bar view by clicking the caret beside the Create (+) button. Select the item and use the Unarchive button in the tool bar highlighted above.
Once a object is unarchived, it will be once again visible in working view and can once again be edited by users who have "Write" access to the project to which it belongs.