I know the "silent scream" emblem says taken King quest reward before you acquire it and you get it by doing something on the dreadnaught. Same does the fatal vision ship so maybe you have to find out where in the destiny universe it can be obtained. As I'm writing this I'm searching each nook and cranny of all patrol location to find that sexy beast.
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I got my silent scream emblem from going into the cabal beachhead ship and finding a secret nook to pass through a door. There were enemies and then a Hive ultra knight spawned in a room off the the side. I killed it and was rewarded the emblem, much to my surprise.