Save As problem
I recently spent several hours on a piece tentatively titled Untitled-4. When I wanted to do a Save as for a new title it saved as alright but replaced the Untitled-4 with a blank script with the new title. So several hours of work was gone in an instant. Previous versions were different. When previous versions did a Save as, they also retained the original piece. This was good if a problem arose the original composition was still available. Not the case with Version 3.0.1.5087. I was so depressed after this that I think I will go back to version 2.1, unless an improvement is made to retain previous version of compositions as well as Save As versions...NOT replace them.
Comments
Update to 3.0.5. Even though the issue you're describing may not be related.
And if going back to Musescore 2, take 2.3.2.
In any case "Save As" does not overwrite anything, not without warning you at least, not in any version of MuseScore.
Both scores are still there unless you did a Save as... and chose the existing score and clicked OK to allow MuseScore to overwrite it. It sounds like you put the score in a different folder than you thought.
As mentioned, the behavior of MuseScore has not changed in this respect. I think whatever you did is something different from what you think you did, and you'd be capable of the same mistake using any version.
If I had to guess, I would say that when you did a Save As on some new new score, you probably gave it the same name as the one you lost rather than a new title, and hence it overwrote the original., That's exactly what all versions of MsueScore, and indeed all computer programs period, do. They want you if you want to overwrite the file, and if you say yes, that's what happens.
Meanwhile, if you did overwrite an existing file and are running Windows and are using OneDrive, you can recover the old version by going to the OneDrive site.
Or, more optimistically, maybe you simply saved to a different folder than the one you are currently looking in.
But again, absolutely none of this has changed in any way whatsoever, it's compltely standard computer program behavior.