Viewing file from 20 minutes ago

Stop using the computer immediately. I (and probably several others) are looking for a solution.

From reading through http://www.google.com/search?q=os+x+file+overwritten+recover+OR+recover,+-"time+machine" it would seem you have a very slim chance of recovering the file, and it will require a third-party program (several are listed in that Google search). No guarantees. The more you use your machine (including hitting the "refresh" button on this page!) and the fuller your disk, the more likely the old version of the file will be overwritten if that hasn't already happened. It only takes changes to a few bytes to make the file unrecoverable. The news is better if you are using a newish SSD with plenty of free space rather than a hard disk.

Sorry, I wish the news were better.