Either of - ‘Didn’t you know?’ or ‘Haven’t you heard?’ – would be the appropriate response.

Off the top of my heard, ‘have + known’ tends to be reserved for discussion of length of acquaintance, as in ‘I have known Mr X for ‘so many’ years.’ (There's more to this but I'm too lazy to consult the instructive texts)

Perhaps the difference in the latter case is merely rhetorical – reflecting speaker impatience, or opinion about the length of time it is taking someone to get something done (in any case, longer than hoped for!).

‘Haven’t you finished yet?’ would appear to be distinctly more impatient.