Page slug getting "-2" appended, would like to change

I have a page whose slug is “buy-cookies-2”. This is a pretty critical URL for the site, but it is getting that -2 appended because at one time there was another post with that slug, but I tried looking in wp_posts, sorted by post_name and found only this page and a menu item for it. I backed up the database, then tried changing the post_name for both of these to remove the -2, but the change didn’t seem to stick. Is there a way that I could make this change and have it be permanent, so that this important URL can look a bit cleaner? Thanks!!