GWT shows 1 blocked url but no warning

I am seeing 1 Blocked URL in my Google Webmaster Tools account since a month ago under Google Index >> Index status (Advanced).
But I am unable to find that actually which URL is blocked ? My robots.txt is the same as it was previous and there is no warning in GWT >> Sitemaps.
I am asking this question because I faced a huge drop in my search traffic since this error occurred. (From 600-700 unique visitors to 10-12 visitors in a day). And this drop happened in a single day after a server…
GWT shows 1 blocked url but no warning

See original post by skin1607