when you ask someone a question and they just stare at you blankly like you didn't say anything

You ask your colleague if he's seen the Henderson file. He stares. You wait. You ask again, slower this time, like you're describing colors to a potato. Still staring. You're convinced he's either deeply contemplating the nature of existence or hasn't blinked since 2019. Then his eyes focus and he goes, "Sorry, what?" — turns out he was just looking *through* you at the motivational poster behind your head.
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when you're trying to tell someone something and they just stare at you with a blank expression like they have no idea what you're talking about

You're mid-sentence explaining why you can't eat dairy, and they stare at you like you've just described quantum physics in Mandarin. So you repeat it. Slower. Louder. By the third time, you're pantomiming lactose intolerance like a mime trapped in a refrigerator, and they finally nod and say, "Oh, so you don't like milk?" Yes. That's the thing I said the first time. In English.

When you ask someone a question and they just stare at you instead of answering.

You ask your coworker if he's seen the Henderson file. He stares. You wait. You clarify: "The blue folder?" More staring. You start to wonder if you've become invisible, so you wave your hand in front of his face—and he snaps back: "I heard you the first time, I'm just deciding if I want to help you."