Thanks for your response. I did some more messing around, and discovered that if I open the file using File->Recent Files, the drawing opens. For me, that's completely reproducible behavior. Not sure why this would happen. Makes a good-enough work around for now.
As for the other item you mentioned, yeah, I'm just getting started in this, still do brain-dead things, and really just wanted the simplest possible test case that would illustrate the issue to upload.