Problem Permalink

A most bizarre problem was discovered today.

A post from 2010, as seen in the Edit Page’s permalink field as: https://tastingroomconfidential.com/speed-tasting-reds-at-2010-wine-blogger-conference/ ?

automatically changes to:

https://tastingroomconfidential.com/2010/07/09/speed-tasting-reds-at-2010-wine-blogger-conference/ when viewed.

In the link window, the link is displayed as the former and creates a 404 error when clicked on.

This may have been the post I was working on when I changed my permalinks from Day and Name to Post Name, as it is the only post in my database that behaves this way.

Currently it is unviewable. How can I manually override this permalink without going into .htaccess?

Thanks for your help.