My opponent played "Come Back Wrong" to kill one of my creatures.
The effect of the spell then takes it out of my graveyard and puts it on his side of the battlefield. This all happened as expected.
The issue was that we both had the card "Defiled Crypt" in play, and instead of me getting the 2/2 black horror creature, my opponent did, despite the creature leaving MY graveyard.
Playing on PC windows. Log attached