I was playing Destiny and I just finished a patrol mission, involving killing mobs to get drops, I forget exactly what it was but it was on Venus.
When I got the last drop I was running towards where the mobs spawned, they were coming out of a doorway when I killed them, and since my cat scratched at the door, I just ducked into the doorway and into the spawn area to have a safe place to stand still while I let my cat in and fed him.
While feeding him I heard the familiar voice of one of the patrol mission givers, and when I got back to the game I had a new patrol mission, involving gathering "Docking Caps" from fallen, and it was already at 33%.
How did this happen?
Did another player nearby pick up the mission and gather some of those items, and since I was close enough I got both the mission and the items?
I went outside the spawn area, and I can't see anyone close by, and suddenly the counter for the item is up to 67%. While I look around trying to figure out what is happening the mission completes.
Note: I was not in a fireteam.