Someone I once supervised listed me as a reference for their background investigation. The investigator called about six weeks ago, and has never answered his phone since. Today, I called and left a message: "You called about the background investigation for $PERSON about six weeks ago. I've called you back numerous times, but this is it. Unless I hear from you, this is the last time I will try to call you."

(The person was not a satisfactory employee. In fact, I advised him to look outside $EMPLOYER. I won't tell anything the investigator does not ask, but if he asks the right questions, the truth will come out.)