You can't remember sex. You can remember the fact of it, and recall the setting, and even the details, but the sex of the sex cannot be remembered, the substantive truth of it; it is by nature self-erasing; you can remember its anatomy and be left with a judgment as to the degree of your liking of it, but whatever it is as a splurge of being, as a loss, as a charge of the conviction of love stopping your heart like your execution, there is no memory of it in the brain, only the deduction that it happened and that time passed, leaving you with a silhouette that you want to fill in again.
Your mind has a way of not letting you forget things you wish you could. Especially with people. Like, you'll always try your best to forget things that people say to you or about you, but you always remember. And you'll try to forget things you've seen that no one should see, but you just can't do it.