Bless you, Sherry! Bless you, bless you, bless you. As you know, I'm an impatient user -- I dig into what I need for the moment, and have little time for other research. I had never stumbled on the Auto Recovery feature, and therefore was trying to rebuild from a 5-day old file, comparing it to a good midi file I had created before my catastrophe -- not fun.
As fate would have it, I was so distressed over my faux-pas that I got paranoid and put yesterday's date in the filename, so my original file's backups were not being pushed out of the bottom of the stack -- a stroke of good fortune. So, of the 5 backups for the original file, number 3 was the final before my disaster. I've lost all of the time yesterday and this morning to my now-unnecessary rebuild, but that pales compared to what I still had left to do (and changes that might not get made again, if the thought didn't strike me again). So, if my opening sentence seems a bit overboard, indeed it is not.
Now, I just need to get back to the final tweaking that I was in the midst of yesterday, before it got dark.
Ralph