It definitely existed but I think only before the 2.0 update . Possibly a change in development strategy and patching phased it out . It was rather strange at how I got it . At the time I didn't even realize what it was

I had the quest line , I stopped playing for a long time I came back about 2 months ago . I noticed I had the unknown patron quest line . Even when I was in crucible it would say " you have preformed a feat" I couldn't find much information on how to do it ... then the next day it updated me to the 2.0 and everything was different an the bounty was gone ... even on my destiny tracker you can see where I had the unknown patron missions ...