I was recently informed by someone that my website was copied. When I looked at the linked that he gave me I so that the site was identic to mine except for the logo and tex
In that case, probably they have an access to your ftp account. If I were you I will change my ftp credentials.
And also, there are tools that would really copy all of the websites content, including its source codes. One notable is IDM or Internet Download Manager http://www.internetdownloadmanager.com/ which has a Site Grabber feature.
There is no full proof way.
But here is some strategy that can be employed to hide source code like using "window.history.pushState()"
Detail here - http://freelancer.usercv.com/blog/28/hide-website-source-code-in-view-source-using-stupid-one-line-chinese-hack-code