The issue is whether there was an attorney/client relationship, or whether the past relationship had ended. Was a fee paid for work that wasn't performed? Or was it simply a lawyer who had done some work in the past?
But from your brief recitation, it is obvious that the former clients could have sought another lawyer's help before resorting to the hand written approach to the document.
I agree with the previous answer. It doesn't sound to me that there was a current, or ongoing attorney-client relationship. The party could have gone to another attorney.