Forgot that I actually had an update ready, but it was for such a minor fix (typo), I hadn't released it yet.
But yeah, I had explicitly set the icon to be the "questionmark.png" found in the base game, because like I said, it never appears in-game. I'm actually not sure how you got that icon to appear, since I've tried using Factory Planner, What Is It Really Used For, and the Recipe Book mods, and the recipe group doesn't appear in any of them.
Regardless, I've changed the icon to the one that appears for the technology, as it seemed the most fitting. I also added the item-group name to the locale.cfg, so the group should appear as "reverse factory" instead of "item-group-name.recycling". Updated for v7.0.10