Thanks for the report, newbiemn! There is no known bug with Black Cat as you described.
1) No, anything that an undo command "undoes" is not preserved in the log.
2) You are the first to report this.
3) It is known that the game sometimes says an undo is for a big amount of steps when it should be only one or a few. The reason is unknown, and likely something else went (slightly) wrong before.
In respect to 3, can you remember roughly how far back the undo went? An "undo" goes back to the last decision the player who requested the undo made. If Stitch 624 asked for the undo, it should have gone right back before she bought the Province. If MrSplashyPants asked, it should have gone back to the point where they decided if they want to play the Black Cat. For the other players, it should have been to the last decision they made, and lookign at the log, that would be the last thing they did on their respective turns.