I'm really sorry this happened to you, but if you don't have Autosave enabled, your work might be gone. Of course I hope you can find it in a temp file. Did you open up Word and see if there's a recovered version? You have do to this from the program.

In future, of course, never do this again. Whenever you start a file, take the time to name it and save it right away. Then when you are blazing along, hit Ctl S every so often to save your work: every time you get up, every time you pause to think about what your next paragraph should be, every time you have a big burst, etc. Make it a habit and you'll likely never lose anything more than a small bit after your last Save.

I know how frustrating this is and that awful feeling when you realize your work isn't there. Arrrgh!