Hi, I'm not sure where you mean by "file", but I've looked in "my recent documents" and it's not there, and it's not on a file search either.... it's vanished from the folder it was saved in?? It just doesn't make sense!
And, this "folder" is on the flash drive, right? Did you have other files on the flash drive? Can you access them?
Such a dilemma should be an incentive to improve your procedures in the future. For one thing, never work on a word processing file for a long time, e.g. for two hours as you did, without doing a save. Getting in the habit as saving often, say, every 5 to 15 minutes, will help prevent such losses.
Also, unless this file is a sensitive document (based on content), I would not work off the flash drive as a normal practice. In other words, save that file to the hard drive and work off the hard drive. Then, when you've finished a session, copy the updated file the flash drive. However, if you prefer to work off the flash drive because you're working on someone else's computer and you want to leave no trace of the file on their hard drive, implement a procedure of periodically backing up the files on the flash drive to YOUR hard drive, or burn to CD, etc.