David
Your question completely depends on the book. At some shops, if 9 innings are played, and the game is rained out in exra innings, the total is graded based on what the score was at the time. At other books, ANY rainout without completion of a game (ie winner) then the total bet is n/a. This even holds true if you bet o9 and the score is 5-5 going into extra innings. If that game is rained out, certain shops grade that play as n/a just as they would if it only went 6.
Check with your book.