I don't think you'll find it on a table in a room, I mean. Looking through the glass at Seige of the Warmind and Promethean code you can see obvious differences in the makeup of that room. I've little doubt you'll have to go back there at some point, but I'm starting to believe the trigger is more relics found out in the wild more and more. Take the quote from GI for example, or what banshee says about the faint beacons sounding like music. In my very unprofessional opinion I thinks there's more relics.