PAA:
This question prompted me to review that section of the book, as well as any other part that could have given any clue. And so far, this question really stumped me. I cannot think of a satisfactory answer. I only have two that are most likely unsatisfactory. But whatever, here goes…
Firstly is one I really don’t like, but that I don’t think is impossible, if improbable. And that is that Harry went back to Ollivander to double check the rule as far as other wands not physically taken are concerned, and the book didn’t inform the reader as had Harry said it explicitly it may have given away the ending.