Nginx using default configuration on its own

I have set up Nginx on Ubuntu server 14.04 I want to configure a very simple server block that listens for /app path and redirects traffic to a running nodejs instance locally.

I have done that with proxy_pass and other proxy settings.

My problem is that all the static content (img,js etc) from the node app are trying to be served from /var/www/html which is the root objective defined in the default site configuration created upon Nginx installation! I have deleted the symbolic link from enabled-sites folder and even removed the default file from the sites-available folder with no result! Even so the root path is serving the default Nginx welcome page which is defined in this site configuration and nowhere else!

Are Nginx defaults defined anywhere else? As long as I create a simple site configuration as simple as server {} welcome page and static content are served as defined in the default file which I have deleted!!! How can I fix that?