I know, been done to death, but there really needs to be a way to get loot back if accidentally passed to the wrong person, and that person has left the quest, especially for quests where people can't get back in.
Tonight accidentally passed the Sovereign rune to the wrong person, The person who wanted it had the rune I had been looking for... real shame someone had to loose out because the rune went to the wrong person who couldn't swap it back... Seen this happen too many times for my liking...
Maybe if you pass something to someone, and they leave the quest, that item reverts to the person who passed it.