In Ticket to Ride: Europe, on your turn you can pick up two cards from the face-down deck, two cards except locomotives from the face-up cards or one from each. When I pick up one card from the face-up deck, it gets replaced right away from the draw pile.
If the replacement card is a locomotive card, can I keep it because if I had picked up two from the face-down deck, it would have been mine?
No, once a card has been revealed as a locomotive, you have to "spend" two draws to pick it up, which means you can't do so since you've already drawn one of your two cards.
From the official rules (PDF), emphasis mine:
If a Locomotive card is one of the five face-up cards, the player who draws it may only draw one card, instead of two. If, after having drawn one card the replacement card is a locomotive, the player cannot take it.
