Revit 2020 not saving files with no errors

[stephanieD6PGL]

upgraded from 2018 to 2020 in January- opened a file created in 2018 in January - Revit did it's conversion thing , I worked on the file, saved it and closed it.  Opened the file again in March to work on it , saved and closed it.  I made PDFs of the pages so I know I'm not loosing my mind on 3/13.  Went to open the file today and it did it's conversion thing again- from 2018-2020.  Then I find that nothing I did on 3/13 is there.  Looking at the file date in the Revit folder shows the date last modified was 1/5-----meaning it did not save the file on 3/13.

Is there some way of recovering this?  There is no logical explanation other than Revit possibly doing some type of update on it'self and deleted my file. 

Any help is appreciated since @Anonymous forces us to pay yearly for their software and give NO SUPPORT for their software and no way of contacting human beings.

[ToanDN]

The only explanation is someone opened the original 2018 file and saved it over the upgraded 2022 file.

[stephanieD6PGL]

Thanks, but that is not the cause.  I am the only one working on all files. What am I paying yearly for again?????  There is basically NO support- not even a phone number to call for issues such as this one.  So over it

[RSomppi]

Revit files cannot be saved back to an earlier release. This HAD to be done outside of Revit.

[stephanieD6PGL]

Thanks for responding, but there is no mention in my problem about "saving back to an earlier release". Very simply: opened a file in RevitLT 2020 that originally was created in RevitLT 2018- worked on the file, saved it, closed the program. Went to open the file again and it was nowhere, the file had not been saved.
After some sleuthing into my hard drive, I did see that Windows did updates on the same day my file was saved- it is possible I left the file and the program open when these updates happened or they happened in the background, but still doesn't explain where evidence of the file being worked on on that day is, or the dated/updated file itself.
Aren't there logs created within the program that I can search for specifically that may give me some clue as to what happened?

[RSomppi]

If the file wasn't saved, then there wouldn't be anything to explain why it wasn't saved.