I just think it would be more logical to leave the clue on a decoy. That's mainly what it's for. But if the clue doesn't connect to the Shaman, why is he a decoy?
Regarding planting the clue on him, I don't know. But you were still in the block.
Even if you turn out to be a Mafia member, we still need to eliminate you. Because Mafia members are as dangerous as the Town.

