Strange hotlink protection issues - .htaccess - .htaccess

Question

I used the rules that should work, and have worked in the past but every variation I try it continues to serve a the image (clearing cache each time). Other rules like URL rewrites work fine.
I would provide a copy of the error logs but I can't seem to gain access to this through FTP, neither can the person running the server droplet.
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http(s)?://(sub\.)?example.com [NC]
RewriteRule \.(jpg|jpeg|png|gif)$ - [NC,F,L]
I know this seems like it should all be working, everyone says the codes are correct. Yet for the past few weeks I have been trying find solutions. I'm positive there is something else going on that is not related to the code, I just need help finding it as I'm not too experienced working extensively with htaccess.
Full htaccess:
ErrorDocument 404 /404.php
AuthType Basic
AuthName "Password Protected Area"
AuthUserFile /path/to/.htpasswd
Require valid-user
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http(s)?://(www\.)?dev.mangazing\.com [NC]
RewriteRule \.(jpg|jpeg|png|gif)$ - [NC,F,L]

Answer 1

Is this what you're looking for?
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http(s)?://(www\.)?sub.example.com [NC]
RewriteRule \.(jpg|jpeg|png|gif)$ - [NC,F,L]
EDIT
Please try to replace your rewrite rule line
Replace:
RewriteRule \.(jpg|jpeg|png|gif)$ - [NC,F,L]
With:
RewriteRule \.(jpg|jpeg|png|gif)$ http://icons.iconarchive.com/icons/tatice/cristal-intense/256/Ad-Aware-icon.png [NC,R,L]
Your code will look like:
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http(s)?://(www\.)?sub.example.com [NC]
RewriteRule \.(jpg|jpeg|png|gif)$ http://icons.iconarchive.com/icons/tatice/cristal-intense/256/Ad-Aware-icon.png [NC,R,L]
Or
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http(s)?://(www\.)?dev.mangazing\.com [NC]
RewriteRule \.(jpg|jpeg|png|gif)$ http://icons.iconarchive.com/icons/tatice/cristal-intense/256/Ad-Aware-icon.png [NC,R,L]
and visit 1 of your image urls, I hope this is working for you.. remember to upload a replacement picture to a server and change replacement URL in the new rewrite rule, this can be done with a transparent 1 pixel image (Not a html/php etc document, it must be an image file!) free hosted at google pages or any other webhosting service you like..
Edit 2
Please try with <IfModule mod_rewrite.c>:
<IfModule mod_rewrite.c>
RewriteEngine on
#Your other anti hotlink commands here...
</IfModule>
More methodes to protect image hotlinking: creating the ultimate .htaccess anti hotlinking strategy