I did have a mother. I know I did

(Grammar Questions I Can't Answer)

So, we continue reading a lot of children's books to my daughter, and my wife (L1 Vietnamese) thinks she found another grammar mistake in a children's book.  (See HERE for the last mistake she found in Green Eggs and Ham.)

This time it's from Are You My Mother? by P.D. Eastman.  After searching everywhere for it's mother, the exasperated little bird says at one point: "I did have a mother.  I know I did."

"Why is it in the past tense?" asked my wife.  "Shouldn't it be in the present tense: 'I do have a mother, I know I do' ?"

I couldn't really give a good answer to that question.

Interestingly enough, however, my wife also caught that their are two different versions of this sentence.  In the original book, it's in the past tense.  But in the Bright and Early Board Books version of the same story, the exact same sentence is now in the present simple.