I have collected all of ymir's tear stones in asgard and completed all but one of the world Mysteries but the tearstone collected from following the herd did not show up in my inventory so I am stuck with 29 out of the 30 stones. I tried loading an old save from before but it still didnt show in my inventory even after saying it was collected

I have collected all of ymir's tear stones in asgard and completed all but one of the world Mysteries but the tearstone collected from following the herd did not show up in my inventory so I am stuck with 29 out of the 30 stones. I tried loading an old save from before but it still didnt show in my inventory even after saying it was collected