Zombie Thread - Arise!!!!
Just to offer (a bit) of conclusion - we returned to this same restaurant this past weekend. We had not intended to be in the area at lunch time, so I didn't have my email correspondence handy (although I was going to try to dig it up on my phone). Anyway, when we were being seated by the hostess, I asked to speak to the manager, and she said "sure thing". In just a minute, the manager appeared (and I was messing with my phone trying to call up my old emails) and I introduced myself. He remembered our conversation (specifically about the sandwich and mayo on the side) and also remembered that he had sent a coupon for an appetizer. At that point, he said "Don't worry about the coupon - let me know what you want and I'll put the order in right now." While he was still there, our server appeared and we talked about what had happened (this was a different server as well).
To make a long story short, my wife and I ordered our sandwich (mayo on the side) and two orders of fries. We got our appetizer, entrees in drinks in timely fashion. The order was correct (mayo on the side) and the manager stopped by as we were finishing up to ask if everything was okay (which it was). The appetizer was indeed free, so I was very satisfied.
Now, the big question is: the next time we go to the restaurant, and I'm just another joe-schmoe customer - will the order be right? At this point, I feel that they have earned the opportunity for me to find out (again, stressing that while I'm not in love with this restaurant, both my wife and son really like it).
Hope this brings this thread to some sort of conclusion, good or bad. Thanks for all the comments along the way.
Good luck and take care.