I have been a restaurant manager in this city, at some very well known and well liked spots, for years, and we all make mistakes from time to time! I wholeheartedly encourage you to share your negative experience with the restaurant. In fact, please do not hesitate to do so.
I always tell our guests who are less than pleased THANK YOU, this is how we grow, taking the good with the bad. As a manager if all I ever hear is "everything was great," I am missing out on the opportunity to learn and grow and in turn, grow my team.
If a guest is unhappy and they've already left us, there is nothing we can do to rectify the experience. Believe me--when we get to a certain level of professionalism, nothing is more upsetting to us than to think there was a problem and we never had the opportunity to address it.
With my staff, I share complaint letters when appropriate in pre-shift meetings (same as I share compliments and kudos), and we talk about what went wrong and how we can avoid the same missteps next time. We look for patterns, if one server seems to get a lot of complaints, we dig deeper. If one hostess seems to put everyone off their feed, we dig deeper. If one busser seems too overbearing, we dig deeper. The guests feedback is of utmost importance to us. I can't emphasize enough that this is how we up our game and constantly raise the bar.
That being said, most restaurant staff are acutely aware if there is a problem with a guest before it gets to this point. Or they should be!
I would recommend perhaps writing a Yelp review coupled with a letter--either snail mailed to management or via the general inbox link on the website--and then amending your review if and when you receive an adequate response. And if you don't receive an adequate response, I'd think twice before dining there again!
But yes: please write to the restaurant and let them know of your experience. For many of us at a certain level, this is our career which we take very seriously. Your feedback, whether positive or negative, is a tool for growth.