If you haven't yet closed the document you could try 'undoing' until you get to a previous state. (Edit > Undo or Ctrl+z)
If you've closed it, go to open it. Before selecting Open, right click on the file and select properties. If its size is zero bytes then you've lost it.
There's an option for recovering files in Word but I'm not up on that. I can look into it if the other options don't bear fruit.
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