Rob K mentions in his answer, in your example A has already defined the context, so "it" is perfectly clear.

However, it is not uncommon to say a pronoun without context, but it is awkward since the listener would not know the reference.  You would have to add some further explanation what you mean.

> A. I'm sorry, it's completely sold out  
B. What are you referring to?  
A. The game.  It's completely sold out.

I don't think this is unique to English, since it's more about the general quirks of pronouns or any ambiguous part of speech.