The woman who cooked a meal that is believed to have contained poisonous mushrooms and led to the deaths of three people gives a lengthy written statement to police detailing her account of what happened, and revealing she was hospitalised after the incident.
It would not be so noticeable after they’ve been dehydrated and chopped up, no. They should still be identifiable as an amanita if they’re dehydrated and not chopped up, but it would be harder. But whoever gathered the mushroom should have been able to identify it as inedible, unless they were very inexperienced (and thus not likely to be somebody who forages and sells to stores).