Are you sure you know where you saved the file to?
Did you save it repeatedly over and over to the same location with the same name?
If so, then there was only really ever one copy of the file.
And if that file was deleted by mistake, corrupted, or is just gone...
without it being in another location also, You won't be able to get it back
How do I make sure it is really gone? How come it would be lost if I saved it?
If your search does not return anything at all, and you are positive of the name, it is likely gone.
There are too many ways the file could have been lost to make an accurate diagnosis.
The file could have been corrupted by the computer being shut down while the file way active.
The application could haev shut down while the file was active.
Either of these could have happened while the file was being saved, or being closed.
You could have a virus or other Malware....
I did not shut down the computer
There are literally hundreds of possible scenarios.
This is the kind of situation where looking for a root cause is kind of fruitless, because there is simply no way to be sure about it.
I LOST THREE HOURS OF WRITING. IS THERE ANYTHING ELSE I SHOULD TRY?
You could always try a recovery program to see if it could find a delete file.
How do I do that?
This program will search for deleted files on your hard drive and try to UNDELETE them
You download the program (Recuva) and search
But I have to stress that this is a hail mary
It is possible that it will find your file, but highly unlikely.
It never hurts to try, though.
You seem to have left.
In the mean time I will switch this to a Q&A format question so you can come back to it at any time. I will also be notified when you make a posting.