为什么我添加到我的.htaccess的重定向规则会消失？

I'm a total newbie so please forgive if it's a stupid question but something weird is happening. I've added custom redirection rule to my .htaccess file RewriteRule ^/?hosts/(.*)$ /user/$1 [R,L]. After some time, that rule is just gone from the .htaccess file. All other rules are in place. Only that rule gets removed. Any idea why?

 # BEGIN WordPress
    <IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteRule ^/?hosts/(.*)$ /user/$1 [R,L]
    RewriteBase /
    RewriteRule ^index\.php$ - [L]
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule . /index.php [L]
    </IfModule>

    # END WordPress

Wordpress will rewrite everything between the # BEGIN WordPress and # END WordPress tags every time that permalinks are rebuilt.

Place your rule above the # BEGIN Wordpress comment:

RewriteEngine On
RewriteRule ^/?hosts/(.*)$ /user/$1 [R,L]

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^/?hosts/(.*)$ /user/$1 [R,L]
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>