A hesitant sheepish smile returned, followed by a chuckle. “Sua,” he corrected.
Or should it be Tua. I am not 100% sure, but I am pretty sure that it should be the informal you possisve form in this case.
Both are correct.

Here at the South we use Tua. But all the other States use Sua.
I find it wrong (sua is the possessive from the 3ª person!), but I live in the only State that speaks Portuguese as it's taught in the Grammar books.

All the other States speak "sua" because they use the pronoun "você" while we use "tu". So we have to bow and accept "sua" as correct.

I believe Portuguese courses teach "você" and its correspondent possessives as the norm because - although we speak the formal Portuguese - we are minority.
Clark visited the North, so "sua" is appropriated. It's what he would hear there. I wrote a long post to Virginia about it with more Portuguese grammar than she would need to know. :p
Andreia