In order to restore a deleted document or spreadsheet, visit your Trash folder located in All Documents. Currently, this feature is only available in Quip's web product.
From your web browser:
Click on the “All Documents” section of the main toolbar.
Scroll to the bottom section labeled “Deleted Documents” & click on the “Trash” folder. Click on the document you wish to recover & choose “Recover”.
Quip will return the document to its previous folder location. Quip will also directly open the document to remind you of that document's location. If the original folder has been deleted, Quip will place the recovered document in your Private Folder.