old page slug permanently inaccessible

hi there,

i have a real mystery on my hands here and wondering if anyone can help. i had a page with the slug of “demos” on my client’s site and the url was this: https://richreads.com/demos

however, one day my client said that the page was no longer working. i’m not sure why, and not sure if he logged in and hit something that he wasn’t supposed to, but i was unable to fix it. so, i deleted it and re-created the page, which named itself https://richreads.com/demos-2/ and i changed the links and that should have been fine. (although the prior deleted slug should have forwarded itself to it as well.)

however, when i go to my old page slug of “demos” i’m not getting my custom 404 page. i’m getting the 404 page for the web hosting company. i’ve tried slug removing plugins, i’ve tried permanently deleting the original page, nothing works. with the help of a plugin, i am now able to create a new page with the “demos” slug, but it still goes to that 404 page with the hawaiian shirt, rather than my own and rather than a new page that i might create. is there some other place i can go to not have this slug permanently inaccessible to the wordpress software? if i cannot use that slug, then fine, but i’d like to at least have my own 404 page there like it does for other situations (such as: https://richreads.com/demos-3)