As you can also read in the linked article, she broke away with some others, as is usual in cycling. After a while the peloton caught up with the breakaways, thinking they're now racing for the lead. But they didn't realise Anna Kiesenhofer wasn't among them, as she is a virtually unknown amateur, so nobody missed her.
Excuse us, she never was an virtually unknown amateur. 2017 she got a professional contract from a Belgian team, but refused to cycle on their "stupid" rules. She rather went by her own rules, without a team and didn't need the money. 2018 she was 5th in the European time trials. She constantly rode, but not so much on professional UCI events, but also on many amateur marathon events. Which she thought were harder and better. She was official Austrian champion afterall.
The peloton just missed her, due to complete lack of communication amongst the disfunctional leading dutch team. There were many dutch and other coaches on the street with cellphones, but they didn't try to catch her, so she was lucky. A properly organized peloton would have caught her easily. You could see with your own eyes how disorganized the peloton was. Extremely interesting case for social studies.
Yeah, I don't mean to discredit her. Just saying the peloton didn't think of her as they caught up with the front runners, as they didn't really know her. Exactly for the reason you state: she didn't attend a whole lot of pro events.
