Bad Circuit Breaker????

Had power (volts/amps) to a circuit...receptacle, small wall heater and another receptacle (all 110vac). My grandson was pulling the plug out of the 1st receptacle....installed a "twist and snap closed" receptacle cover. He kept pulling the plug out but it snapped closed.

Lost power to all 3 (2 receptacles and heater). Same circuit where plug was being pulled out. Have replaced the 1st receptacle, all lug connections, no back wiring, still no power. Checked everything with voltage checker and wand...nothing. Checked all breakers (on/off test and tested with wand) not finding a bad breaker. Bought a Breaker Finder/Tester. Will that be reliable in finding a faulty breaker, if that's the case? Don't want to start pulling breakers out unless I'm fairly certain.

Any other thoughts or ideas?

Thanks,

Bob---PA