I ended up deleting the post somehow, so I don't know what I said. They had sex in a flashback, if that's what you mean. I just realized I have the scenes at the beach. The ones I'm missing are Roof A, the two after Bass Guitar (I have no clue what those are, so it's possible I didn't see them) and the flashback after Love. I followed the walkthrough, so I wouldn't have gotten anything outside of that. If there was a scene where they had sex in the present then I didn't get it. :P
EDIT: Okay, I think I found the problem the walkthrough says July year 2 or later. I extended the time until the AMPs by spacing out the scenes since they start in May but "By the Pier" requires it to be at least July. Even when I do that, I still matter have nowhere near enough time to activate the scene. Between the time I finally get Beach II, it's almost time for the AMPs. If I hang out with Dallas, I can only get one scene a week. I don't have enough time to get "By the Pier" because the AMPs automatically start. It's impossible, unless I'm doing something wrong. It's a shame because I'm really curious to see the scenes. I think part of the problem is that those scenes don't count as required scenes. I'm forced to go to the AMPs after triggering all of the romance scenes, but since those don't count there's no guarantee I'll get them in time, if at all. I've tried about five times, and it isn't working for me. The time limit is too short.