I removed it best I could, and wiped it down with a bit of vinegar. It was very dry, fell right off no residue. I think it was from when the substrate was still a little moist. I checked around and didn't see much more just a few tiny bits. I also cleaned and checked around the water dish, it was a bit damp from being covered and there was nothing. He/She was very good, sat and ate a meal worm and watched me.
I would think as long as I keep it nice and dry, I should be okay. I have it sticking around 50% humidity, rises a bit at night.
I'll keep a good eye on it, worst case scenario new substrate, baked in oven. And another good vinegar wash down.
Agreed, just mold, remove it as best as you can. Keep humidity low so it doesn't start growing again in case you missed some.
I've had much less problems, nearly zero, since switching to soil years ago. Photo of how I dry a 1 cubic foot bag. Takes a day, but the house doesn't smell from using the oven to dry it. Plus no energy cost, sunshine is still free.
But, to each their own when it comes to what they use as substrate.