If it's too deep to be detected, it's awfully hard to hit it with a drill. The original Aerotem survey that indicated a conductor was not replicated by VTEM, so they did a Pulse EM. At least, I believe that all to be true. The latter two methods did not indicate a conductor of any significance, or so I have been told.
It's hard to know what the truth is, but I believe the bullseye would be a priority target if the geophysics indicated that it might be a nickel sulphide deposit of any size.
Lar