With his two consecutive flukes, Satoru had established his identity as someone related to the boss. And the kidnappers genuinely believed it as fact. That's why no matter what Satoru did, he knew that the kidnappers would believe him. His flukes were foolproof, and it gave him an exceptional amount of confidence even though he was weaponless.
He was just a regular kid and the kidnappers had superpowers, as well as guns in their pockets. And yet he held the most power in front of them.
Luck was on his side.
The next thing he did was grab his phone, and then he briefly told them about the situation. With this, the police wouldn't make a mistake and blow Satoru's cover— this was what Satoru feared the most since the police might come to the place guns blazing, sirens blasting.