Vargoth goblin prank glitch

So... Please help me explain this:

With Vargoth up, I played Goblin prank on a minion, and it recast on vargoth himself at end of turn, but (as expected, same as Soularium interaction) he didn't die. Excellent. Even better, he survived to my next turn.

To my surprise, when I pressed end turn, he instantly died!! As if the Goblin Prank effect triggered a turn later! I certainly felt pranked, to say the least!

(P.s. I don't run goblin prank - picked it from marked shot) 

In Hearthstone, "end of turn" effects are only triggered at the beginning of the end of turn step, not in the middle of it. Goblin Prank kills a minion when the end of turn step begins. When Vargoth cast Goblin Prank, because the end of turn step had already begun, Goblin Prank did not kill him during that turn. The Goblin Prank buff lasts until the beginning of an end of turn step, at which point the buff kills the minion, which is what happened. This is the same reason why Vargoth casting Shadow Essence and getting Lich King/Ragnaros won't trigger their effects immediately. Y'Shaarj works the same way.

Thanks for the reply!

Do you know what happens with Vargoth + the Soularium? I know the second set of 3 cards drawn are not discarded because of the mechanic. But do those cards get discarded at the end of the NEXT turn? Because that is the equivalent of what happened with goblin prank.