No, the term “rain check” by definition implies that the date is unknown. The term actually derives from outdoor event ticket sales. If, for example, you paid for a ticket to a baseball game, but on the day of the game it rained and they were unable to play, you would be given a “rain check,” which would let you go to a different game on some unspecified future date.

No. In fact, you never would. The word "raincheck" implies some future date that is unknown.