Write a letter complimenting the employee on handling of difficulty.

Dear Sir,

This is to inform you that I have been informed about your associates in the shipping department of the incident that occurred last Thursday with a representative of Gene's Tool Supplies. I have been told that this driver used foul and abusive language directed at you and that his actions were unjustifiably offensive.

Your colleagues informed me as how  you remained calm in the situation, rather trying to solve the problem. I compliment you on your self-control, and in deft handling the situation in such an exemplary manner. I have placed a call to the owner of Gene's Tools and fully anticipate that you will receive an apology from them.  

Thanking you