Website Replica crawling issue

Dear Warriors,

I wanted to know that what will be the possibility of get crawled and result if anyone have created just replica of one his own website?

This question comes in mt mind while one of my friend is discussing about it that one of his client have create 1 website and place the same code with everything similar to another website on same server.

Now Google shows one website in his search result and 2nd is not even crawled which was almost 3 months old.

I've suggested him not to do that to prevent to be penalized by Search engine due to duplicacy.

But is there any way to know what is the exactly problem or signal that Google not crawled his website even if his (my friend's client) is not implemented any redirection code, canonical tag, robots.... nothing related to seo points of view was implemented on both of the sites. As my friend's client is a lay man in terms of seo. He doesn't know anything about it.

Please share your experience.

Thanks in advance.