Yessir, I've done all of those and the game does give a warning when I go to the murcard cave to meet up with scar.
what happens with the choices and what are the choices with the warning? because that should be right before you start the event to progress the conspiracy storyline is and there shouldn't be anything stopping you from just saying your ready and getting into the event.
also just a sidenote, try both at day and night for whatever option you pick in case it's that. not saying it is but I've fucked up and completely forgotten some stuff is based around the games time cycle and struggled for like any hour lol.
"under the cover of night" just means after 20:00 but before 0:05 in game time lol. and yeah, but rereading your last thing, have you done the thing where you explore the cave with Scar alone? because if you haven't my bad I completely misunderstood where you were. and the option should show up at the cave as "meeting point"
and no one has met yet her lol. she's just spoken a lot about by over half the NPC's in game involving Northcrest XD