missing preference file

I generally save files to a specific folder my computer (not the cloud). I was able to edit and I thought I was saving along the way. I saved right before closing the file, then got an error message about not being able to back up b/c file in use. But there are no other users, I am the only one. Since I'd just hit 'save' I just said don't save and shut down. The next day I went to open the file and nothing I'd typed the day before was there. Had to start all over. I am thinking I may need to contact Microsoft for assistance but if you have any suggestions, I'd love to hear them.

Sorry to be the bearer of bad news, but since you chose to discard the changes, they won't be saved anywhere.

For future reference, if you get a message that a document cannot be saved, try to save it under a new name, to make sure that you do not lose data.

I am not sure about the underlying issue here. Your description suggests that temporary files that have been left behind from a previous session are preventing you from saving, because Word interprets that the document is already "reserved" for editing by someone else.

Save As should work around this, temporarily at least. You would have to give the document a new name.

However, there may be a more serious issue with saving (permissions) that must be dealt with separately.

Deleting the settings files will not necessarily help in the situation you described.

Where are you saving the affected document? If you save to the dedicated documents folder in macOS, then can you edit the document as expected?