This is actually covered by the Gatherer rulings for Sylvan Library:
If you choose to draw two cards, then replace one or more of those draws with some other effect, the rest of Sylvan Library's ability still happens. If you've actually drawn only one card that turn, you must choose that card and either pay 4 life or put it on top of your library. If you haven't actually drawn any cards that turn, the rest of the ability has no effect.
You did choose to use the Library's ability, so the other part will still work. If you haven't drawn two cards that turn (because some effect replaced the draws), you'll do as much as possible. You've drawn one card this turn (the card you normally draw at the beginning of the draw step), so you'll have to pay 4 life or put that card back.
Nathan Long
Wizards.Com Boards NetRep
Edited Nathan Long (May 19, 2015 07:40:01 PM)