As Arnie controls Sulfuric Vortex, so he is responsible for remembering the triggers from it. Sulfuric Vortex is a symmetrical ability, so we can take whose turn it is into account when determining whether or not the trigger is generally detrimental.
When the trigger is missed during Newt's turn (by explicitly moving to the Draw step), it is not a generally detrimental trigger for Arnie. Since we would not issue an infraction in this case, we do not intervene.
When the trigger is then missed during Arnie's turn (by drawing his card for the turn), it is generally detrimental for Arnie, so we intervene to issue him a Warning for GPE - Missed Trigger. Newt has the option of putting the trigger on the stack at this time. It is also worth asking a few pointed questions to ensure that Arnie has not intentionally missed his triggers, but given that he just missed it on his opponent's turn as well, it is likely he has indeed simply forgotten about the Sulfuric Vortex.
Edited Vincent Roscioli (May 22, 2013 12:06:45 PM)