I see the AI Oracle Ceresa kill a bear, but she doesn't have enough movement to take the Signs of the Bear goody left behind. I move some custom scouts on to the square to try to deny her the prize and bring a hero to claim it for myself (our relationship is Close and I figure she won't attack just for that). However, next turn, not only does Ceresa takes the goody, but my scouts vanish into thin air. No combat. No declaration of war. No message of any kind. Just... poof!

I have a saved game where I can reproduce this if you want to see it.