I'm using ewiki and create new pages using [...].Thanks for your suggestions, Frank. I tried them out, but unfortunately with no success. Creating a new test page and linking to it from another page did work, so presumably there isn't a problem in the wiki. Using the page's history and 'fetch-back' didn't resolve the problem. I didn't try out Idea 2 because there are lots of links from the orphaned page and it would take me at least an hour to re-create them.
However, if I can't resolve it soon I think I'll have to give up trying to sort it out and will in fact have to re-create all the links again from scratch