Disappearing Page

A page that has been up for well over a year, and which I could access a couple of days ago has started to return the front page (index.php) of posts when selected in the sidebar page list (where the URL is correct).

The underlying URL returned shows the page permalink correctly but has #513 appended, which is the most recent post number.

I have checked all the page’s fields in the ‘Posts’ table and in the ‘Postmeta’ table and they are all correct.

I have updated my permalinks without success.

And I have done a search here bit didnlt find anything pertinant.

Any idea what has gone askew anyone?