If you don't understand something then you're in the perfect position to improve the docs. Others who are already familiar with the project may not think they need to document it, because they see it as simple.
I've even gone as far as forcing the developers to answer questions by incorporating new information into the documentation. If you start having out-of-band communication (email, chats, in-person conversations) between the newbie and the team, there's a strong chance that extra information will never find its way back into the documentation.