I would say so. They do mean different things, though, and I suppose the question-setter thought A fit the context better. The tricky thing here is that "I didn't think" doesn't actually mean what it seems -- that it never occurred to you, as in A -- but rather that you thought about it and you concluded the contrary. To put it another way, the "not" negates the proposition about bringing the gift, not the act of thinking.

B seems more natural to me, but both are correct