where to put the conditional when "if" is omitted?

Edit [Moderator]: Link removed

If I were you, I would call her. --------> Were I you, I would call her.
If I had known, I wouldn't have done it. ---------> Had I known, I wouldn't have done it.
--> In these cases, the result clause cannot come before the conditional clause.
(I wouldn't have done it had I known.)
(I would call her were I you.)
I am an English teacher in Korea. I sometimes study English grammar on the above website. And I have taught English grammar like the above as they teach. But lately, some of my students took an exam for being a civil servant. And I found one of the test questions reads as follows, which I am sure is grammatically incorrect according to what I have learned from the website. But they asked the students to choose the grammatically correct one, and the following is the answer.
*Tom might have been like that throughout his life, had he not found his son.

In this case, how can I contradict that the sentence is grammatically incorrect? in addition to the website?
Would you give me more information to support that the sentence is grammatically incorrect?