Well, that's unfortunate. Thanks for the report. That location has been a bit odd since the new owners took over a few years ago. They have yet to find a concept that works for them, and Gustav Burgers is their latest attempt.
Without hearing the conversation I can't comment on what the difficulty was, which could be anything from the waiter's ear not being accustomed to your particular accent to his English being non-existent or worse than your French. The important thing is that you made an effort to communicate in French, and that they had someone available to communicate in English when that didn't work out.
I can say that I've gotten a few odd looks when my pronunciation and annunciation have been imprecise. For example, there's the French word for lightning, foudre, which I've used, but has been heard by others as the French f-word (substitute "t" for "d").