I thought I remembered the 'ground' category in particular having a lot more substances in it a few months ago - were all the 'Real Displacement Textures' removed from 'Substance Source'?
As an example, 'Forest ground with roots and needles' is still available under my personal 'My assets' tab, since I previously downloaded it - but no longer appears anywhere else on the site.
Be a shame to have lost them, though I assume there were some licencing costs.
