Strangely enough, asking him what he last remembered was a weird question. Clearly as day, he remembered fighting the Titans with the gods, and defeating Gaea. But clear as day, he also remembered the first time he stepped foot in Camp Halfblood. With having been told by many people what happens in his future, he couldn't exactly say what was the last date he remembered.
"It was definitely after we got Gaea and saved the world. And that we knew Leo's ass was alive and chillin' with Calypso, but... definitely before I actually met him again after he returned. I mean, Apollo was here in this world for a bit so he told me what happened somewhat..."
He could have went on explaining how he knew about a Meg that Apollo met and their whole plan to save the Oracles. That much he knew from Apollo and also Rachel Dare. But he couldn't really continue after Jason muttered the D word. Percy wasn't sure what to say after that, but as his brain scrambled for words, he stared out at the road for a few seconds.