ladyred - it sounds like the one you can't find is the one that's hiding in a small alcove. When you are in the area between the Temple and the Exit to the city gates, you would be able to hear this one because he's right behind the wall you are near.
To get to him, stand with your back to the temple, and look toward the exit to the city gates. (The city gates are where you originally found the Tripodon.) Look along the wall, starting at the exit to the gates, going right, until you see a small alvoce you can enter. Looks like a dead-end at first. Find the sandscraper in there.
If you have no luck, there is an eighth one you can get. The eighth animal is in the Sanctuary of Memory square, just trotting around. If you need this one, because you couldn't capture the one that runs away, be sure to exit the square and trade it to the merchant before you go see Vel Subek inside his sanctuary.
Finally, what you get in return for the sandscrapers is a magic Tuning Fork. It makes you invulnerable to attack for a short time, but it is not essential to get it, because there are spells you can cast for the same effect.
Please feel free to e-mail me with questions, since I don't often check the rpg forum.