There might be something wrong with the .material coding itself if it disapperars. It used to disappear for me if I messed something up, even though the folder itself wasn't deleted. If you could PM me the .mat or post it here, I'd be glad to look at it. If you're sure it is not the material, maybe try switching your game's randering system or reinstalling. Make sure you save all presets, maps, etc somewhere else so they aren't lost. :3
Aye, as stated above, if the preset 10 doesn't show up in game then there's something wrong with your material file for it. A quick and easy solution to solve this is copy the material file for preset 1 and paste it in your preset 10 folder. Make sure to change the name of the material file to 10 instead of one, and go inside the actual material files and change all the 1's into 10 :P