Laboratory Maniac did not proc
I was Jace, opp Serra. LM's Miracle triggered, I played it, and soon summoned Frost Giant on top of it since it was spent. Lost the game when I outdrew myself.
Edit - Another Jace game lost due to this broken mechanic. Vs. Kiora this time, so it doesn't look like a Slinger-specific issue.
Achirae#26937 shared this idea