It would be good if the "Contact Us" feature had the option to post a topic in a dedicated forum (chosen by the Admin) to allow the Admins / Moderators to respond and ensure the query has been dealt with, it would act as a log for the Contact Us application opposed to (and perhaps in addition to) the message being sent by email.

That’s called a ticket system and it is in fact already available as part of the IPS Community Suite and also tied into the Contact US function. But it’s a functionality of the Commerce app. You need to have that installed. 

I have created an app for this

 

Another option: