I loaded up a map (Miner Evacuation Speedrun Zerg), and many units, including the minerals and vespene, are invisible. They show up in the Existing Unit Palette Editor, but the text is blue, and the "Visible" column shows "<Yes>" for the invisible units, and "Yes" for the visible ones. They also don't show up on the minimap in the editor. They don't show up as selected unless I enable "Show Hidden Selections", but I can't find anything about show/hide unit in the editor. If I test the document, they are all there and visible.
I've reset the editor settings, tried everything I can think of under View/Render/Layers, and nothing.
I did a replace of the minerals with rich minerals as well as a replace of the gas with rich gas. The replaced gas showed up, but only a few of the minerals showed up.