Red dirt or dust is not much better, maybe even worse, I bought my prado like 7 years ago from a government auction place. It looked pretty good, well cleaned and detailed, I saw in the service manual it was base in Emerald, country Queensland, I should have known there would be red dust and marks in most of hard to seen places. I gave up trying to get it all out.
Yep, that red dust is impossible to get out of a vehicle completely. I'm not surprised it was still in there or that it got in there in the first place. I've been to Emerald, Q. a few times and there's red dust everywhere.