Rewrite causes Sitemap Spider to Fail

I am using this rewrite rule in my htaccess. RewriteRule ^blog/([0-9]+)/.*$ /blog.php?post_id=$1 [L]

For some reason when I go to create a sitemap via Create your Google Sitemap Online - XML Sitemaps Generator

It spiders pages that don’t exist and keeps add pages to the url in the wrong way… for example…

mysite.com/blog/5/blog-title is a real url
mysite.com/contact is a real url
mysite.com/blog/5/blog-title/contact is NOT a real url

Is the rewriterule causing the issue? I just want to make sure google’s spiders don’t have the same problem.