fraudulant collection wont go away

[Netals]

What is the name of your state?Washington. Many years ago (1999) my husband introduced a friend to one of his neighbor who was selling a car. His friend bought the car but didn't get the title because the people had to get it out of their safe deposit box. A couple days later the car broke down and got towed. The friend never bothered doing anything because it was a $100 car. Months later my husband was contacted by a collection agency saying he owed for the towing bill. He tried to explain that he didn't own the car and was told that the neighbor had told the collection agency that they sold it to him. His mother tried to take care of it. She contacted the Dept. of Licensing and even got a noterized letter from the friend stating he was the one who actually purchased the car. She sent all of this to the CA (and didn't bother making copies) and they said it would be taken care of. All was well other than getting rejection letters when applying for car laons and credit cards ( he assumed this was because he had no credit history at the age of 18 ) Recently our isurance agent mentioned to me that our rates would go down if we got a collection that was coming up on our credit report taken care of. I acquired a copy of our credit report and found the collection from 1999 was still on there. I got copies of records from the DOL showing all vehicles that have ever been in his name (the vehicle in question was not on there) and wrote a letter to accompany it saying that if that info was not sufficient then I wanted them to validate the debt in writing and inform him of what documents the needed to resolve the issue. I sent it certified and got the confirmation of receipt in the mail two months ago. How long should I wait to get a response and should I just hire a lawyer to take care of this for us? Any other suggestions appreciated. Thank you.