So get this...
I finally complete your ridiculous quest step "lock and key" for the radiant phaseglass...
I see the quest complete, I see the radiant phaseglass pop up on screen, I leave fireteam before countdown finishes, go into inventory IT'S NOT COMPLETED, AND MY RADIANT PHASEGLASS IS GONE, AND TO TOP IT OFF THE LOCK AND KEY MISSION MARKER IS GONE....
WTF DO I DO? IS WHAT I'D USUALY ASK, HOWEVER IM CERTAIN THAT THE FAULT IS YOURS BUNGIE...