I don't know when I stopped working yesterday, but very likely I saved a file before shutting down my computer.
How can I find the (not system owned) file with the last save timestamp?
Show a finder window sorted by date modified.
Open a File Menu > New Finder window, or Cmd ⌘ N
If 'All my Files' isn't the default, View menu > All my Files or Cmd ⌘ Shift ⇧ F
Your most recently saved file will now be at the top of the list.