Quote from TDHSolomonAlright, like I thought. Then let's take another look at the original question:
Q: I cast Nevermore and name Howlpack Alpha, because I lost to it last game. A little while later I realize that's pointless - you can't even cast Howlpack Alpha! Am I in trouble if my opponent tries to cast Mayor of Avabruck?
Suppose the opponent wants to cast the Mayor and a judge is called to resolve this situation. What is the judge supposed to do? Try to read minds and find out whether or not it was clear to all players that a shortcut was taken?