No, no written threat.
However, my former employer called me and asked me to return his call. He didn't even wait 24 hours, the next night he gave his attorney my home phone # and had the attorney call my home. The attorney left a message. He didn't say what it was regarding, but did say that (employer) asked him to call, and said it was 'extremely important' that I call him the next day. He said it in that 'bill collector' tone of voice that makes it seem like I better call or else.
Well, I am two things...I am very 'not push aroundable', and I am very literate and good with the written word.
I called the ex-employer immediately, told him off for sicking the lawyer on me, and told him I would take care of his lawyer too. I then typed up this excellent letter; you would swear a lawyer wrote it (I should post it here for your enjoyment), instructing him to cease and desist any communications with me, or it would constitute harrassment. I also explained my position, and how all of his problems he has caused on his own.
Then, just to add insult to injury, since I have a personal relationship with the building owner (the project we were building) I informed him that I would do whatever I needed to do to help the client, but would completely sidestep him (employer) in the process.