Percy found out that Apollo had a forgotten child that was exiled from camp half-blood because of the visions they got from their prophecies that so happened to come along with being a half-blood of Apollo. He found out from Will that the forgotten half-blood lived out in the forest by the camp and that Will was still in contact with them just to make sure they were okay. So,In true Percy fashion,Percy went to find them

It wasn't too long before he smelt fire burning and He found a not too shabby camp ground,which wasn't really a camp ground,it was more like a hideaway. Then,he saw them..He flinched because he didn't see them at first,but they were still wearing the iconic orange camp half-blood shirt so he was bound to see them sooner or later

"Oh,Hey! I'm Percy,You must be that forgotten Apollo kid.."