If you fail to move the king out of check (for any reason) what is the status of the game? I will start by saying I am new at chess.

The scenario is as follows. In a particular game you are in check, but fail to move out of check because you and your opponent did not realize this. Since the rules of chess state that you must not take any move to leave yourself in check or put yourself in check, what do you do? I read that for FIDE fast paced chess they have a stipulation that benefits the "checker"(ie you messed up... sucks to be you). Is this a house rule that everyone abides by? I cannot find anything pertaining to this mistake elsewhere.

Thanks.
FIDE Laws of Chess, 7.4.1:


  ... If during a game it is found that an illegal move has been completed, the position immediately before the irregularity shall be reinstated. If the position immediately before the irregularity cannot be determined, the game shall continue from the last identifiable position prior to the irregularity. Articles 4.3 and 4.7 apply to the move replacing the illegal move. The game shall then continue from this reinstated position.


So, based on your/your opponent's written recording of the moves, the position will be restored to the last position before the illegal move. Articles 4.3 and 4.7 refer to touch move - in replacing the illegal move, you must move the same piece that made the illegal move, unless that piece has no legal moves.

In addition:


  For the first completed illegal move by a player, the arbiter shall give two minutes extra time to his opponent; for the second completed illegal move by the same player the arbiter shall declare the game lost by this player.