I agree with the OP's sentiment that it's incredibly frustrating to go out looking for a hunt only to find it living up to it's billing on Ariyala as "missing" because it had been killed and unmarked. That being said, it's entirely possible for hunts to be killed by people who simply don't know what the deal is (A ranks, at the very least). Most anyone familiar with S rank spawning, in my experience, knows to call them out and mark them, and that's experience with hunting on two vastly different servers (in terms of how grouping and relaying is handled).