Nothing is earned in this game. I've gotten a total of six Ghorns, one is fully maxed the other is getting there. The other four have become shards. I got them all from RANDOM encounters, vanguard ROC or NF and one came from Crota on normal. Nothing in this game is earned UNLESS you saved up marks and bought gear from he venders or it's an exotic bounty. So the thorn is earned (imo) as is the bad juju and so on. The Ghorn is not a earned item. I have friends who have played double the amount I have and still don't have one. It's all luck. I say let Xur sell it so elitist pricks like you no longer feel special.