Didn't a later report say that an employee put the device there to find out when his supervisor was going to show up at work? (Or was that the "cover story")
Was that the excuse that was given for the sensor device? The last offical explaination that I heard was that someone accidently dropped the device on the tracks, which I promptly noted as BS becauzse the device had been painted black to blend in with the ballast and was partially concealed.