Mis-spelled copyright footer and couldn't amend it. Copied work to date and pasted it into a new score to get by the problem. Original score not in background (?) but I carried on. End of day did final 'save' and was prompted again to save (?) when I closed the window, so I did. Was asked if I wanted to replace the existing file, which I did, because the file on-screen was the correct one, so I clicked 'yes' but the file saved turned out to be the old file. Lost a day's work. The Revert To option does not appear in file menu as advised by Apple. The second request to save must have related to the original file in some way. I've been on Macs since 1988 and have never experienced this before.