For those curious, this was Dave’s Sushi in Bozeman, MT. Very sad and scary. It appears that food storage and handling had a role here.
from my research on morels a few years back when i found some growing in my back yard unexpectedly... all sources seemed to say you need to cook them to neutralize or lower the toxin that may be present in them to safe levels. never ate them thou because the ground wasn’t one i’d consider pristine enough to eat from.