This is a very interesting case.
I know if your reading, you probably think that it's nothing really to worry about...but, if that certain "Crew Person" still works there, I'd be very surprised.
What I'd do to is
1. Go to the store again, and complain to the Shift Manager (you may think this is worthless, but it works out to be very rewarding!)
2. Tell the Shift Manager about the incident, and he/she will record it in a Complaints File (the reason why it's rewarding is because that complaints file gets sent off to Head Office, I know, because I work at McD's Australia) Australia goes by McD USA standards, so there is no difference in procedures.
3. Head Office SHOULD contact you about the incident and you CAN get something rewarding (i.e: money, 1 years unlimited free-meals etc...)
I have in front of me the "McDonald's Australia (USA (C)) Policies and Procedures" Booklet.
It claims that what he done was NOT up-to standard (no duh...)
This excerpt was taken from "Customer Service" section
"......customers, however, may wish to recieve a non-priced beverage with their McValue Meal (i.e: soda water, chilled water), this must not be refused, but MUST be charged the correct price for the meal...."
I wish you luck in getting this problem solved!!!