The attack you're describing is a typical automated thing where hackers are exploiting dozens of devices in some automated fashion, that can happen but the damage is different. They might get your data but that's usually sold on the black market in a bundle of compromised data. It will take some time for the info to get sold and for the buyer to act on it and sometimes it may never act - after all you're one compromised device among millions. Even if the buyer it's more likely he'll simply use your device in a botnet to fake clicks on ads or DDoS something and profit that way. The key aspect of those attacks is that you've time to flag suspicious activity and act.

However if you carry an unlocked phone and someone steals that from you there's a very high chance that it isn't a random burglary, according to statistics most burglaries are committed by someone who knows victim aka is targeting you specifically. If you're targeted by someone or some entity they'll want your data and accounts and they'll have the time, resources and attention focuses towards you giving you little to no time to react. This is why I would NEVER use a phone without a secure bootloader.