I’m in the middle of an epic duel with a fearsome foe. Unfortunately, he reduces me to 0 hit points and I fall unconscious right beside him. My wizard-friend tries to finish him off with a spell, but our opponent counterspells. Before my turn, my trusty bard-friend heals me with a healing word and I’m back in the fight. On my turn, I stand up and evaluate my chances. I decide to flee.
Do I know that my sworn enemy cannot take an attack of opportunity if I move away without disengaging, even though I was unconscious when he used his reaction for counterspell?
Or more generally: Do I know if someone already used their reaction?