My first games of new expansion today, but I am pretty sure how this should have worked:
Me: Hunter
Opp: Rogue.
On Board: 2 Rogue minions, 1 Hunter minion.
Rogue had Kidnap secret in play (along with 2 other secrets).
I played a Click-Clocker (which had +1/+1 buff on it in hand). I did not have a mech in hand for the Battlecry to buff.
The Kidnap secret triggered.
Sack was not summoned.
The Click-Clocker (with it’s 2/2 stats) just remained on my side of the board.
Two turns later, opponent left game. Game was still close - I figure he was frustrated on his secret not working properly.