Tell me please which tense is the most apt to use in the following context.
Rob, do you often drink soft drinks? I haven't thought about that.
Rob, do you often drink soft drinks? I hadn't thought about that.
I heard native English speakers use the present perfect in similar contexts. But wouldn't it be more grammatically appropriate to use the past perfect. Because Rob hadn't thought about that before the other person asked him a question. If both sentence equally correct, explain me why please.