No. I had a Year 1 Thorn in the vault and last week I got the Year 3 Thorn bounty. I was patrolling the Plague Lands near the Ketch just filling some bounties and it just appeared. I hadn't even turned in a bounty when it dropped - just boom - there it was. I fill all sorts of bounties regularly, like new ROI ones, Crucible, Queens Wrath, COE and Vanguard on all 3 characters. So it appears to be random drop and only my Titan has received it. Hope you get it..