I'm so sorry this happened to you. :( If my 6 year old save file all of a sudden went missing I would be so sad.
Would you consider to set your whole computer back to a earlier date, where your save file was still there? It is the last thing I would try and it is a bit drastic, but if the save file is so important it is worth a try.
But before you try this make sure to save every important changes and papers you made/worked on in the meantime somewhere else on a an external save card or something.
Hopefully this was understandable, english is not my first language.
I hope you will somehow get your savefile back.