A few months ago, I made the mistake of clicking through from Google Flights to the Ryanair website in order to book a flight with them. A few days later, they sent me an email saying it had been booked via a third party and asking me to confirm my identity (costing, I think, £5) or check in at the airport for something like £30-£40.
Since then, I still use Google Flights or Skyscanner to compare flights & prices, but I always make sure I open the Ryanair website separately and clear cookies and history before I book anything (or use the app).