ask your guy how long ago the shrooms were harvested. if they were kept "not quite cracker dry" in a sealed plastic bag, there is a high chance of mold (unsafe). there is also the chance that the fruitbodies were not harvested in a timely fashion, causing them to become old and spongy, possibly "fuzzing up" with living mycelium that is trying to jump off the fruits onto a new substrate (safe).
home-grown shrooms must be produced in a clean environment, and most growers keep dust and potential mold spores to a minimum in their homes if they don't want to lose their grow to contamination. as long as the fruits got dried quickly, there is almost 0% chance of contamination. field shrooms is a completely different story, as they can be found in any state of decay with any kind of life growing in/on them.
while it is true that cooking does not destroy certain toxins that molds (black/green/pink etc) can produce, i am certain that you would be able to identify truly moldy shrooms, they look just like moldy bread or pizza. if you are seriously concerned about the quality of the product, then throw them out. but i would personally chop them up (don't grind, it makes a mushy mess) into little chunks, then pour freshly boiled water over them in a mug. squeeze a little lemon juice in and drop in a bag of herbal tea. steep 5 minutes and drink. re-brew the remains for a second cup, and i'm sure you'll be right as rain