Possible bug in FilterControlledPermanent (likely LKI issue with sacrificing a stolen permanent)

Order of operations:

- I cast a [[Threaten]] effect to steal [[Thunderbreak Regent]], correctly taking 3 damage from Thunderbreak Regent.
- I cast another [[Threaten]] effect, using mana from [[Ashnod's Altar]] sacrificing Thunderbreak Regent to cast it, targeting [[Atarka, World Render]] (opponent's commander, in case it's relevant)
- Thunderbreak Regent triggers upon me targeting my opponent's creature, even though I controlled Thunderbreak Regent at all relevant times.
- I checked Thunderbreak Regent's code, and other than a typo about Slivers in the code it appears to be implemented correctly, which suggests to me that the problem may be XMage seeing "Thunderbreak Regent was in play when this spell was being cast, and it was owned by my opponent, so it should trigger when one of their dragons was targeted" even though it was under my control when sacrificed.