Which reminds me, shop assistants can't be relied on, either - even female ones.
Was in my local Asda, queueing at the checkout, when I heard an elderly-ish man (probably about my age ?) asking where the Dijon mustard was.
Assistant, looking slightly nonplussed: 'Oh, we don't stock it any more.'
I thought that was weird, so made a detour to the condiments aisle and there, right at eye level too, were 3 different kinds of Dijon mustard.
Went back to the bloke and showed him.
I suspect that either the assistant couldn't be bothered, or perhaps had never heard of Dijon mustard and so assumed they didn't have it.