Yes, the same thing happened to me. They were looking for my ex-husband and they thought it was my son.  I did not give any information about him and the main claimed that he had been bought up on charges and that they wanted to find him.  They called relatives and said the same the thing to them and they refused information also.  They would not tell me what type of charges they were; however, he stated that this was the same as being served.

Same deal, calling at work, talking to co-workers, asking for protocol of our company regarding dropping off , or serving papers.    Talked to them several times, he said he was a private locator, no company name, nothing, can't give anything in writing.       Called the ACLU, was advised to file complaints at the Ohio Attorney General (my state), The FEderal Trade Commission, the local police, which I did.....

Gave me an 800 number to call, once i started asking questions, said he wasn't supposed to, i called, told me they can't send, email, or provide me with any documentation, which as a consumer, it is my right.  
The ACLU said it is illegal for them to contact you, or show up to , your place of employment.  Also, when I asked for information about the company, I was hung up on several times, finally someone told me this is a pre- litigation company....which , the ACLU rep told me was a collection agency, using illegal methods to put people into a panic.    

My locator, was John Dalton, which we all know is not a real name....but just an fyi....he also refused to give me his call back number, said based upon what he does for a living, can't take incoming calls.....really?

Call your local ACLU, free legal, State's Attorney General, and the Federal Trade Commission to make a complaing!!!!!!!!!!!!!!!!!!!!!!