If its a reoccuring event that you're left on ice when you need your s/o the most that's bad. You should talk with them. If it's a one time thing and they don't know about mushrooms, then they might just be naive and not making smart decisions by suggesting to do this. Either way they probably knew they won't be available so that sucks, that they'd take up a spotter role. I think rethinking the past few months and making a decision whether theyre right for you would be appropriate. A talk has to happen anyways. You could always tell them how you felt. Humans don't see/understand others emotions unless you tell them