"Trip free" circuit breakers typically refers to a C/B mechanism that will trip and open the circuit even if the operating handle or knob is held in the closed position. That's pretty much standard in aircraft (and many other applications).
Also, in reading through this thread, it appears that the Captain claims to have checked and found no open C/Bs. The open breakers were found some time after the landing. Its possible that with a landing such as this, a fault may have occurred and tripped something. That's not something the crew would be likely to notice at this point (what with landing the plane and kissing the ground, etc.)