That's all interesting, but it only happened with certain mulch presets. I deleted the broken forest object, and made a new one and chose one of the chocolate mulch presets, and it came in correctly with V-ray material, as expected. Yes, I have had it set to automatic and V-ray is always the scene rendered. The other FPP objects all were coming in correctly, but suddenly this oddness occurred.
Unless someone broke into my studio and changed my scene, I see no reason for this to have happened in a few isolated cases, in a scene that's been fine for over a week.
I'll keep an eye on it and if it happens again, I'll post here.