Who is calling me

some guy called me and said that they were investigating someone who has given my name as the reference. The problem is, I did not know the "name" of the person they were referring to. In fact, it did not even sound like a name. I told the guy that I have no idea what or who he is referring to and put the phone down. I checked the phone number in the reverse directory and it came out to be a number that did not exist.