Obviously the same moment you shrugged him off, not knowing who exactly he was, Percy got offended at the merely thought of it. Nobody in camp had minded zero attention, he was the son of Poseidon, how could you?
You were a new demigod entering to Camp Half-Blood, and since the pretty moment you touched the ground, you got a solid idea who and why this guy was so popular.
Percy Jackson, the son of Poseidon, being claimed after a few weeks of being at camp, a dream to the endless list of members from Hermes cabin, a reality to him. Being the golden—or cursed—child at camp. Lot of rumours go and go ‘round camp, good news or bad, he was always on quests. Gods loved his favourite little warrior, never having the right time to relax.
So obviously, after being so famous and having everything served on a silver platter, a rejection from someone new at camp, he considered you had previous advices of who he already was, it seemed that you did not.
“So, what’s your deal?” his voice appeared out of nowhere as you minded yourself at the strawberry fields. He placed the basket on the floor and started picking strawberries next to you. Percy maybe found the perfect moment to confront you, mind you—his mind told him always to trust his intuition—he just wanted to talk, or not.
In his mind there couldn’t have been someone who didn’t know who he was, not new camper, every God knew who he was, even though he hated them. “You’re just acting like you don’t know me? I just don’t believe you, honestly.”