Many people, at least once in their life, find out after messing around. Because when you f around you're going to find out. That's just the laws of the universe. This can happen at any age and any place. That's right, your toddler most definitely has messed around and eventually found out, just as much as your Karen co-worker has -- it's a different process for everyone.
In this situation, a man assisted in helping a co-worker find out. He worked in tech as a project/program manager. He was very respectful, thus was well respected in return. So when his wife was diagnosed with cancer and had to go through chemotherapy, his team and superiors were very understanding and allowed him all of the out-of-offce (OOO) time he needed. His wife would get her chemo treatments everyday for a few hours, so every day he made sure to put his OOO auto-reply on so he could give his wife 100% of his attention and just be there for her and to support her. Everyone was respectful of this for him... Well, everyone except one very entitled co-worker, a sales rep. For some reason, he believe an OOO message did not apply to him...