DT,
can you explain in more detail what you mean by "lost" tail rotor. Did he/she lose the tail rotor gear box and blades, lose tail rotor control, or lose tail rotor drive.
The exact emergency procedure is different for all of them.
However, the vertical stablizer has a function to act as a air foil and produce thrust to help maintain streamlining of the fuselage. This unloads loads the tail rotor, the horse power that would have been used to drive the tailrotor is now avialable for the main rotor to use for lift and thrust. The streamlining is most efficent at some airspeed, probably in the neighborhood of 60kts, that the designers have determined. The streamlining should allow the helicopter to be landed with out tail rotor contol, or drive with a smaller pucker factor margin. The exact procedure is individual to the type of heliocpter, so this is a generic statement of the function of the vert stab in tail rotor failures.