I just noticed that I accidentally unjoined the bar lines in the piano part of an orchestral score by selecting one in Engrave mode and deleting it, so the bar line no longer joins the two staves. How do I rejoin the barlines after the fact?
That should have created a signpost. Select the signpost and delete it.
Thank you @Craig_F. That did it. The sign post was at the top of a large score and off my screen.