The OP has not said what he used to verify the breaker itself. A 100 watt light bulb on clip leads is what I would use to put an actual load on the breaker.
Anything else is subject to argument. I can't think that a staple in the wall would burn thru a wire without something smelling or light flickering or tripping the breaker itself. So for starters maybe the OP can tell us what he used to verify the breaker itself. Then, we can proceed with further advice.