I've tried to find a solution to this problem but I haven't found anything that works.
So I talked to Maven about the plan. Then the frosts lineage papers was checked, but still I don't have the papers. Now I've stolen Frost, emptied the lodge stash (No, the papers were not there), every phase of the quest is checked, but there's no arrow pointing what to next. Also, I can't find Louis to return the horse.
I can fail the quest by killing Frost, but apparently I can't complete quest. I'm playin with PS3, and the save points are so far away that I can't/don't want to "rewind" the game.