So if GJ has Baelor in play, would this effect Robert Baratheon's ability? My thinking is that I could still play the event in the discard pile because it doesn't say "as if the event card is in your hand" but rather "as if you just played it from your hand" so there wouldn't be a check to see if the event card were in your discard pile. Am I right?

That's a tough one. Robert doesn't actually take the event out of the discard pile.

Here's a question for you. If you had 2 copies of the same event in your discard pile, would Robert let you play copy 1?

I'd suggest sending that one to FFG directly just because there is a bit of a paradox that it is both in the discard pile and considered not in the discard pile at the same time.

I sent it to FFG and have yet to hear a response.

Thinking about it more, since Baelor doesn't allow you to play events in your discard pile, and KotS Robert doesn't actually take the event out of your discard pile, it wouldn't be allowed, regardless of whether or not there were multiples or a single event card there.