Killing a creature creates a copy of it on top of my deck

[DivideBy0]

I've noticed a few times that after killing a creature during the opponent turn with a direct damage instant spell before its "enters the battefield" ability can trigger, I would draw a copy of said creature right at my next draw phase even if it's not a card included in my deck.

For example, the attached screenshot depicts such a situation: I've killed my opponent Rainbow Knights with Searing Spear right after they've been summoned, thus before their "enters the battefield" ability could trigger, and I've drawn a copy of them right at my next draw phase. My deck doesn't contain any copy of Rainbow Knights!

So, summarizing:

- Opponent summons a creature with a "enters the battlefield" ability during his postcombat main phase;
- The creature is killed with a direct damage instant spell before said ability could be triggered;
- A copy of the dead creature will be created as the top card of my deck.

I've attached a savegame even if I assume it will be of limited usefulness, as it starts on my turn instead of my opponent previous one.

Thanks.

[DivideBy0]

It happened again, this time after I've killed opponent's Hero of Oxid Ridge with Pitfall Trap.

Attached a screenshot & savegame.

[DivideBy0]

I've managed to create a savegame during opponent turn that allows to easily reproduce the issue.

Simply load the savegame, exile Whirler Rogue with Isochron Scepter right before its "enters the battlefield" ability is triggered as shown in the screenshot, and you'll draw a copy of it right during your next turn.

Thanks.