It has happened in the drive-through.
It has happened over the phone. 
It has happened through email.
There is a well-known coffee joint we use a lot. Whenever we go through the drive-through the lady on the other end always says “drive up hon” or “OK, hon…come on up.” I get it. She is just trying to be friendly.
I had an office call me to schedule an appointment. A direct quote, “Ok, hon I will be sure to send out the paperwork and an appointment card will be attached so you won’t forget.”
I am involved in networking with vendors. When a vendor refers to me as hon it drives me nuts. I received an email that said, “thanks for the information hon, if I need more I will let you know.”
When working in a professional manner I am a strong believer that your speech should reflect your position. If I am trusting you with my food, my money, or my product I want to know that you know how to communicate.
Hon. One simple word. Hon is what my mom calls me. Even though I am a grown adult I will forever be her daughter. She can call me hon. My husband calls me hon. Usually when he can’t find something. “Hon, do you know where the dog food it?”
It is now used in the professional world. Did I miss the memo?
No , simply no , not professional at all
I must agree , “hon” is not at all professional
I haven’t noticed it, but I think it is often more of a southern thing. As time goes on, people are supposed to realize what isn’t acceptable anymore to most people and edit what they say accordingly. I’d say wait til a little time goes by and make a call to the cust service, HR or appropriate area, and let them know that calling someone “Hon” is inappropriate to many, and even quote an article or two. Change needs to happen at grass roots, as sometimes people don’t realize something is offensive until it is brought up in an edifying way so it can be a teachable event.
Drives me nuts. Especially when it’s some kid young enough to be my granddaughter.
Totally unacceptable , “hon” is definitively not professional and and unwelcome at work