Wow!!! that is what you do to your clients, receive the check under both names and then without asking your client sent by mail his part and everything is OK? You better read the below comments from other lawyer ... it will help you to keep out of problem...

I agree that the attorney's actions do not sound ethical. Because we do not have all the facts, however, I agree that you should warn him first by telephone as well as by mail. Even when I receive my portion of a check separate from my client's, my practice is to call them in, even after they have carefully read the settlement agreement. I make a copy of my check and give it to them as well. They are completely entitled to be assured that I have done the right thing.

Ooops I misread the call of the question. It doesnt sound right. I don't know what to tell you besides leaving a message about his ethical obligation and filing a complaint with the bar. You cold also make a claim against his liability insurance.

Would you please explain me the "claim against his liability insurance", it sound very interesting to know this part. Thanks

You can call and ask the bar how to do that if you are going to file a complaint anyhow.