Grasshopper opens previous file version

Have been working on a .ghx definition for a week. Today Rhino and Grasshopper open, I choose to open the file from the main Grasshopper menu, the file that opens is in the state from four days ago. The last four days of work nonexistent. All additions of nodes missing, organization, newer port assignments, etc.

Any clues as to what might of happened and how to recover the work?