This is going to come across as much more critical than intended but I think someone needs to slap you around and point out the real problem.
You act like YOU are the one that is 16. You approach this as if the only two options available to you were to not talk to this girl or to pursue her as a sexual conquest. How immature is that? Seriously an adult can have a conversation with a young person of the opposite gender without being a groomer.
Your first mistake was acting like a child instead of a grown man and not talking to her father and her mother. Your "no-eye-contact" policy and trying to avoid further conversation probably just made you look even more creepy.
You could have acted like a grown-up and involved her parents in the conversation, offering to help her with professional connections or any other numerous possibilities. You could have easily steered the conversation in a way so that she and her parents understood that you were not interested in her in that way. Hell, you could have just straight up put a lampshade on it and said "Hey you're 16 are these your parents? Hey is your daughter really any good at boxing?"
Whatever you could have done, you had a million options but you stuck with the one that made you look to be the worst kind of pedo, the one that was hitting on their 16-year-old daughter but then when he saw her parents were near he backed off. So from their perspective, if they hadn't been there...
Sure it's good that you didn't pursue her, no-duh, but you don't get a pat on the back for that. And I notice that it sounds like you are probably still following her on Instagram, so you really didn't cut off contact did you?
Ultimately the problem is with you. From the moment you saw her, you only saw that girl as a sexual object. Think about that. That was her entire value to you as a person, as soon as that was off the table, you devalued her to not worth your time and even a potential danger. All you saw was a girl with a 'taut' and 'oh-so-womanly' body. That is the real thing that should make you cringe.
