Triggered ability of Jon Irenicus, Shattered One is not working as intended

[[Jon Irenicus, Shattered One]].

Player A has Jon Irenicus, Shattered Mind in play and takes control of Player B's commander with [[Agent of Treachery]].

Player A donates Player B's commander to player C at the end step with Jon's trigger.

The issue: When Player A loses the game the stolen commander was returned to Player B who owned it, even though it wasn't under Player A's control at the time the player lost. It should've stayed with Player C.

Start by locating the Java implementation of Jon Irenicus, Shattered One and the game logic handling donated commanders when a player loses. Reproduce the described three-player sequence, then verify that the commander remains under Player C's control after Player A leaves the game.

Written by the indexing model from the issue text.