Apparently, knickers for girls aged between 2 and 8 are highly sought after, and that is why John Lewis on Oxford Street has not had any in stock the last two times I have been there.
AIBU to think a large department store should make an effort to up their buying efforts and try and make sure they have this basic item in stock. And not say "oooh, lots of people ask this" and giggle inanely when I query it.