One last chance would be to try in the temp folder where blender does some auto backups.
On windows that would be c:\Users\YOURNAME\AppData\Local\Temp ( if you don’t see the “AppData” dir, enable “display hidden files & folders” in windows settings. )
it usually contains some blend files named numericaly where you might find an older version.
If nothing is there or you are using another architecture and/or OS, lookup in Blender > File > User Preferences (or Ctrl+Alt+U) > The “File” tab
That would show the different dirs Blender is using and amongst them the path of the Temp directory ( where autobackups are stored )
In the very worst case there are many re-topology tools, features & techniques to redo a low-res version in no time even from very complex meshes.
-EDIT- Also, an even faster method to find the folder containing the autobackup files, Research a file called “quit.blend” on your computer, the other backups would be in the same directory.