This happened to a coworker of mine a few years ago. The lost document was, as I recall, quite important (we were working for Egypt's Supreme Council of Antiquities). This is what I instructed her to do, and it worked:
Apple menu > Recent Items > Documents
If you see your doc in the list of items that comes up, click on it. It should open. Then immediately do a "save as" (but just be sure not to "save as" back into the trash or hidden folder).
If it's not there and you haven't emptied your computer's Trash since the document disappeared, it is very likely there somewhere. One suggestion would be to take it to a nearby Apple Store with a Genius Bar or some other authorized Apple repair facility. They may be able to recover it for you.
I might be able to come up with other possible solutions. Which OS and which Word are you using?
In any event, besides using DropBox, flash drives, and the like, buy an external hard drive and make daily (or or more frequent) Time Machine backups of your entire computer. I tell you from experience that it may well save you a world of grief.
Another thing to try, perhaps: Each day, or even more often, when I am working on a manuscript of any kind--fiction or nonfiction, my own or a client's--I do a "save as" with a date. If something happens to the particular Word doc that I am working on and it is irretrievably lost, I have never lost more than one day's work, because the previous one is sitting there, unopened. So I wind up with, for example: NDoyle-As_By_Request-141228; NDoyle-As_By_Request-150118a; NDoyle-As_By_Request-150118b; NDoyle-As_By_Request-150119; etc.
Good luck, Gettingby. I feel your pain!