I have known someone for 6yrs and they recently reminded me that they once slapped me, what should I do?

I met this person 6 years ago and we still have a profound connection, it is not often that we talk but when we do, so much is said and felt by both parties. I have always thought very highly of this person, and I haven't ever been able to shake them out of my brain and this person remembers everything that we have ever even said to eachother and the sound of my voice despite the fact that we have not spoken in 2 years. I wonder why? Last week we spoke again and the person rminded me that they once slapped me, which until that point I had completely forgotten, I'm not quite sure how this sits with me, or whether it is even an issue since it did not seem important enough to remember. I haven't mentioned this persons gender, as I dont think it is important. We weren't a couple, and the event in question happened 5 years ago. Is this a danger sign of some kind? Am I over-reacting/under-reacting? All your ideas will be appreciated. What is the best thing to do?