The same thing happened to me. I had just finished the war table operations part and talked to Rat in the tavern, got the next operation, and completed it. A waypoint was supposed to have appeared on my map and also a log in my quest journal. I had also just unlocked Iron Bull's "Demands of the Qun" quest in the Storm Coast. I didn't realize completing his quest first would automatically fail the Sutherland mission...so I went to the Storm Coast with Iron Bull, which triggered his quest, and of course after completing it, the game teleported me back to Skyhold for the post-quest conversation.
I headed back to Storm Coast to complete the Sutherland quest, but could not find it in the map, nor in the journal. I checked here and found out why...Then I checked my completed quests and saw it there, with the explanation: "This quest is no longer available." No real reason why, though...
I get that, from a story standpoint, Sutherland and his company need help, so it's sort of a limited time type thing, but the same can be said for other missions in this game, along with war table operations, that they're "limited time only," and yet you can start them whenever you want (for the most part). I really wish I'd have known about this before... I'm not sure if this is intentional or not, but it kind of sucks that I couldn't complete the quest myself. "This quest is no longer available" isn't a great explanation, either... something like "you didn't get to them in time" might have been better, if that's what BioWare was going for. I've seen the youtube video showing this quest, and I'm guessing there's not much more to it after that, except for one more war table operation, and then I guess you speak to Sutherland again, etc.
--update: I spoke to Rat, and it seems that Sutherland and the others are in fact dead, if you complete Iron Bull's quest first. So, yeah, didn't get to them in time. Or maybe, and this is more likely (and I just thought of this), it automatically fails if you do one too many other quests or operations after getting the quest to save Sutherland and the others. So in that case, my bad...and now I'm sad, lol