Q: With That’s Mine (That Be Mine, Twist Of Fate) played out of turn, if someone uses the Steal a Keeper card, will this Surprise card allow you to take the Keeper they have just stolen?

A: No. They didn’t actually play the Keeper card, they simply got possession of that Keeper by playing an Action. All you could do here would be to stop the Action itself using the Stop That! (Avast! Belay That! The Stars Are Wrong!) Surprise. Using that would not gain you the Keeper they were stealing. It would only stop them from stealing it.