Truffles

I asked this under a different section probaly should have posted it here.
A neighbor uses green grass looking indoor outdoor carpeting in as a weed barrier/walkway in her greenhouse. For the last two years at seasons end she removes the carpet for cleaning and has had truffles growing under where the carpet covered the ground. They don't grow anywhere else in the greenhouse just under the carpet. Has anyone heard of this before? The walkways are comprised of the pumice pine duff that is common here.

do you have any idea what the species is? are there trees growing close by? my understanding of truffles is that they're mycorrhizal, though I don't know that it's always a relationship with a tree.

I've never heard of anything like that, but it doesn't sound too strange to me. I'm sure the carpet-y stuff keeps is nice and moist under there, and the duff provides a nice substrate for fungus.

Mainly ponderosa pines. Species I have no idea, yet.