Do I need to reveal the card I drew from Discipline that I reacted to Sabotage with?

Yes — that drawn card is in your hand when Sabotage resolves, so you reveal it and it's fair game to be chosen.

Sabotage's reveal, choice, and recycle all happen together as one action during its resolution — and "reveal their hand" means all cards in hand at that moment (Rule 425.3.a). Your Discipline resolves first (last in, first out), so the card it draws is already in hand and joins the reveal.

Note what Discipline does protect: Discipline itself leaves your hand when you play it, so it can't be chosen. Only the card it drew is exposed. Sabotage also isn't blocked by the fact the drawn card is new information — cards in hand aren't "targets," so nothing prevents it from being picked.