Thanks to all who replied with your great ideas — you gave me several other things to think about and try out! I’m happy to report that the solution has been found! It turns out that it was a style problem — the paragraph style I applied to the text acted differently on the left-hand page from what it did on the right. I got to the bottom of it by placing the text rather than dragging it, as suggested by Mike Rankin in the second link shared by David above. This pulled the text in as “normal” paragraph style and appeared fine on the left-hand page where I wanted it. Trouble started when I applied the selected paragraph style — poof! the text disappeared again! I undid the style and manually set it — now all is well.

I appreciate everyone taking the time to help me out, and for your generous spirit to a “newbie”!