Here's a good one: the AI stole my
Geth, Lord of the Vault with
Sower of Temptation. Then it used Geth to pull my dead
Lava Zombie out of my graveyard and onto its side of the table.
When prompted to bounce a creature for the
Lava Zombie's ETB effect, it bounced Geth - which went to its hand, not mine.
I was playing in dev mode, and looked in the AI's hand to confirm. I also know that the AI's hand increased by 1, and that its deck did not contain any copies of Geth, to eliminate the possibility that it had a Geth in its own hand and the one on the battlefield just vanished - which would have been an interesting bug in its own right.
Edit - when I later forced the AI to discard that Geth (with
Order of Yawgmoth), it went to my graveyard.