EDIT: I actually had the gun already somehow, even though I never played Guardian Games before. I guess I must have bought it from the kiosk before it was removed. Please disregard this post. I don't have the Heir Apparent - it's the only exotic I'm missing. I talked to Zavala who sent me to talk to Eva. Eva asked me to gather 100 Laurels. I finished this part and talked to Eva again. At this point she had me complete a contender quest, which I did. At no point was there an exotic quest at Eva. Even now. I've checked on all 3 of my characters. The only quest I have is "Medal Case", but as I understand it, this is not part of the Exotic quest chain. The only thing I can think of is that it bugged out when I decided to switch characters while collecting the 100 Laurels for Eva.