I'm not sure of your method in removing it. It's like saying you can't scoop all of the poop out of a little box. The poop doesn't soak into the sand rather, it gets covered in sand and forms clumps - that's what makes it super easy to rake out and I've had no issues getting it all out. It's also why I periodically need to replenish some of the sand - because I'm tossing out whatever sticks to the poop.My experience with sand showed me that you can never really get all the poop out.
Traction sand is about 3 parts sand to 1 part gravel (small various sizes of gravel) it's not a super fine sand. What type of sand were you using?