My sitemap disappeared!

Hi

My website is WordPress and I have Yoast plugin
I disable Yoast sitemap and make my sitemap manual and add it on Public-HTML file on Hostgator

after 2 days it disappeared !! then I add it for the second time and disappeared too!

where is the problem?!!

Thanks

You might be interested in this: https://www.blackhatworld.com/seo/sitemap-is-a-myth.1107910/

(Sitemap may not be necessary if your site is small)