This has happened a couple of times in the IPA league I am in on Magic Online. I have a Shackles on a creature with a white land untapped. My opponent uses a card that requires a sacrifice as part of the cost(ie Death Bomb) saccing the creature the shackles is on. By the time I get priority the Shackles are in the Graveyard. I think this is because his paying of costs for the spell doesn't use the stack but I want to be sure I am not missing a stop. Thanks.