GeoTrust Seal: Internet Explorer not showing the padlock icon for security

Today, I experienced a very weird issue with a site using GeoTrust seal on Internet Explorer. One of my site was showing the padlock icon only for a few seconds and then it would disappear. Additionally, Internet Explorer wasn't showing the security warning "this page has both secure and insecure items."

So after investigating I found the issue to be related to a mod_rewrite redirect. Basically all requests were being redirected to a new URL and the image on my site was using the old URL.

The fix was easy, once the problem was identified. I simply added the following lines to my .htaccess file.

RewriteCond %{REQUEST_URI} !gif$
RewriteCond %{REQUEST_URI} !jpg$
RewriteRule ^store/(.*)$ http://url.com/store2/$1 [L,QSA,R=301]

The above site was working fine with Firefox.

Shouldn't IE show warning if it experiences such a situation, instead of simply removing the padlock?