Variable from list not iterating or triggering if= condition

I want to count the turns in this game of Battleships. I tried to get around the local variable referenced before assignment problem I had by using a list, since I observed I can reference and alter my board list just fine. It's updating the list, as I'm seeing my turn counter climb, but it's not triggering a "Game Over." Why?

from random import randint

board = []

for x in range(5):
    board.append(["O"] * 5)

def print_board(board):
    for row in board:
        print " ".join(row)

print "Incredibly Simple Battleship!"
print_board(board)

def random_row(board):
    return randint(0, len(board) - 1)

def random_col(board):
    return randint(0, len(board[0]) - 1)

ship_row = random_row(board)
ship_col = random_col(board)
print ship_row #erase after testing
print ship_col


def play(guess_row,guess_col, turn):
  if guess_row == ship_row and guess_col == ship_col:
    print "Congratulations! You sunk my battleship!"
  else:
    if turn == 4:
        print "Game Over"
        return
    if guess_row not in range(5) or guess_col not in range(5):
        print "Oops, that's not even in the ocean."
    elif(board[guess_row][guess_col] == "X"):
        print "You guessed that one already."
    else:
        print "You missed my battleship!"
        board[guess_row][guess_col] = "X"
        print_board(board)
        print "Guess again:"
    print "Turn ",turn,":"
    guess_row = int(raw_input("Guess Row:"))
    guess_col = int(raw_input("Guess Col:"))
    play(guess_row,guess_col, turn + 1)


guess_row = int(raw_input("Guess Row:"))
guess_col = int(raw_input("Guess Col:"))
play(guess_row,guess_col, 0)