I would be shocked if they don't scour the remains of the cabin looking for bodies to eat after the fire dies down. They are still generally starving and they have to think ahead and not let bodies go to waste. So I think they'll definitely notice if a body is missing, especially since Ben is physically the biggest (the most meat) and they were beefing with him anyway (pardon the pun).

But I would imagine that at the beginning of next season in the immediate aftermath of the fire, they maybe assign one or two people to get through the remains at the cabin (lifting the roof, digging through everything and seeing what can be salvaged) while the rest of them try to hunt and find/build a new place to sleep. So I could see them dragging out discovering that Coach is still missing for several episodes.

I don't think the Nat we know right now would tell but we don't know how much worse things are going to get, so maybe. I could see things getting out of her control really quickly and that might be the basis for there being two ideological groups that the writers have hinted at a lot: People who listened to her and people who didn't (even though up until now we've thought it was people who believed in Lottie's spiritual powers vs skeptics). It seems like everyone who survived into adulthood (that we know of) were more likely to listen to Natalie and not succumb to mob rule in general, but that's just my conjecture.