A rotor catch assembly for connection in a workstring in a wellbore is provided. The rotor catch assembly is connected to a downhole motor assembly that includes a rotor that is driven by a fluid. In the normal operating state of the rotor catch assembly, fluid flows through the catch assembly and causes the rotor to rotate. In this state, the catch assembly generates pressure pulses in the fluid in the workstring to facilitate advancement of the workstring in the wellbore. In the event of a failure of a mechanical connection in the motor assembly, the rotor catch assembly shifts to a catch-activated state in which the motor assembly is disabled.