I came across this today, and believe that it is a bug:
... Gah! Well, I thought if I pulled the log, it would show the cards available within the Black Market deck, but apparently it does not. (Does Council Room once the gamelog is mined?)
Edit: Here's the log anyway, as you can see where Iso gets confused. Look at the constraints.
http://dominion.isotropic.org/gamelog/201204/29/game-20120429-121817-49fc819e.htmlprohibited: Fishing Village; bane: Fishing Village
Mind you, when I put in the constraints on the main page, I did NOT put any prohibits in - Iso did this itself.
Anyway, I've set all the constraints for 10 cards, one of which is Black Market. I've also specified what I wish my Bane Card to be, if Young Witch appears inside the Black Market. On my 3rd Black Market play, I draw: Tournament, Fishing Village, Young Witch (This is rather irrelevant, but it's how I noticed the bug). Fishing Village was my bane card, and IS on the board. If I purchase it from the Black Market Deck, I can obtain 11.
Thoughts?
--Double Edit-- Put the wrong Game log in at first, correct one is there now.