When I'm in a multiplayer mission and then quit, I forfeit any XP and cash that I might have earned.
Tonight, I played a MP mission and used a rocket launcher to kill a Banshee and a Brute at the same time (I was very proud of myself), but then I got an important phone call and had to quit the mission. I was a little sad about the XP loss, but I was quite sad about my missile. But then I thought, "Maybe my missile didn't get recorded as used if I didn't finish the mission?"
When are consumable items such as medi-gel and rockets marked as expended during a multiplayer mission, at the moment of use or after the mission is over?