Key missing from "Go With The Flow" treasure hunt
Played in coop mode (I invited a friend) in case it matters. When starting the treasure hunt "Go With The Flow" we opened the box in the cave to start the mission. No problem here. My partner zipped across and picked up the key but the yellow diamond didn't go away. There is no key for me to pick up so we can't complete the mission... it keeps saying to take the key. Even in solo mode now there is a diamond on the rock near the fire but I can't pick anything up.If I go to the cave endpoint I can't unlock the door.
I've done multiple story missions since and gone back, but no can do... the yellow diamodg is still sitting empty on a rock with no way for me to activate. Is there anyway to reset this treasure hunt to the beginning so I can complete it? Thanks.