There is one in the other underground temple area that doesn't contain the frog and bird statues (just check the walls, one is false and hides a secret area with one of the black/white runes). And there is one in the small area to the right of the right entrance/exit to the main area where you take all the other runes back to - exit right from that area and then go right and down a bit to the small area and check the left wall to find the secret place with the black/white rune.

It's pretty hard to describe locations in the game, so anyone who needs help can always post here for more help or message me.