Cool scenario. Simple, yet there's a lot going on.
One of my first thoughts was, does Out-of-Order Sequencing apply? MTR says no:
Nor may players use out-of-order sequencing to try to retroactively take an action they missed at the appropriate time.
Then, I thought, it seems like there four different penalties going on: MT, GRV, LAEC, DEC. No matter which one(s) we apply, it seems like the penalty and fix is the same: Put the Swamp back on top, shuffle it in with the rest of the random portion of the library, ask N. if Nancy wants Abel to play the trigger, and Abel gets a Warning.
Yeah, LAEC doesn't apply for reasons previously stated.
MT won't carry a Warning regardless. Like Bob, it's not usually detrimental.
So, is it GRV or DEC? I'm going with GRV. The difference between GRV and DEC is, was there a violation of the CR that preceded and resulted in the drawn card? Yes. He resolved a trigger at the wrong time. It says to do it during his upkeep, but he did it during his draw step.
However, there's that one little example in the description on DEC that keeps getting me: drawing off of a Howling Mine that is no longer on the battlefield. Is this situation analogous? Abel is resolving a trigger that he doesn't exist. But it's not exactly the same. In the KP scenario, the trigger existed, but was played at the wrong time. In the Howling Mine example, the trigger never existed.
So I'm going with GRV, but I'm not 100% on it.