I have never heard of returning a house, but I guess with the right legal counsel you can do anything these days.
I would invest in getting a complete set of drawing/plans from the builder of your model. On those plans should be the HVAC design—if not, request and pay for a set of plans for the HVAC too. That will give not only you, but everyone here will have a better idea of what you purchased. All these plans will be invaluable in the future. Do not expect to get these plans for free.