2007~2015 Antifreeze leaking into engine please advise

My wife and I bought a 2015 CX-9 brand new 5 yrs ago, today I took it to the dealership because my check engine light went on on Friday, dealership said Antifreeze has been leaking into my engine for a while, and that I will have to get a new engine, how can that be, no bells have been going off in the car to tell us of the problem? What can I do since we bought it new?Is it badly manufactured parts?
Unfortunately this is a known recurring issue with these ford based engines (happened in ford cars as well). That being said the engine is under warranty for 5 years so you may be lucky and still be under warranty...