And related to exactly when cards are done being played, how exactly does Industrial Revolution work? Does the card ever go to the discard pile? By my reading of things, you first play the card completely, including putting it in the discard. Then you check to see if you rule, and if you do, you take it out of the discard into your hand. Of course, in real life the card will never physically make it to the discard to save time.
But if this is right, this causes problems. What if you have Gang of Pickpockets in play, and the draw deck is empty? The played card should be in the discard pile when GoP makes you shuffle to draw, shouldn't it? So then how do you get the card back in hand? This seems like the exact type of situation for which Dominion created the Lose Track rule. How does Industrial Revolution avoid "lose track"?
Obv. you mean momentary cards; there's no issue here for perpetual cards.
Since Industrial Revolution doesn't have an ultra-confusing "instead" wording, yes, the card is put into the discard pile and then Industrial Revolution fetches it out. In practice the deck is unlikely to empty, ever, even with 5 players, let alone to be empty at the precise moment it matters here, though the players could obv. arrange for it to happen. Gang of Pickpockets would resolve first and Industrial Revolution would fail. The players who emptied the deck would be unlikely to play it that way, which is fine by me, that isn't spoiling the game for them. The intention was that Industrial Revolution was "instead," but again that kind of thing confuses people, so it's not great to do it to cover an exotic situation, and in this case it's extra messy since cards by default go to one of two places. I did cheat wording-wise with Nomad Camp, but I can't here, the rulebook specifically says to finish resolving the card, which includes putting it into the discard pile or into play.
If you Trinket a card in Industrial Revolution, you can get back the Trinket even though another card would be covering it up in the discard pile. The rulebook doesn't even address looking through the discard pile; in practice I allow it as long as someone isn't being a nuisance.