Purple Jaime, it has happened to me as well...but on Patrol while at the Cosmodrome! The small building to the left of the starting area, if you go down the stairs...as soon as you round the corner into the dark, you are met face-to-face with Acolytes & a Minion who has a sword. Mind you when he dies it says to pick up his "rifle", but the fact that I get to weild a Sword of Crota is pretty cool.