He didn't care if he had to pry her out of JJ's hands and drag her by her shirt in order to come with him. Charlie was going to get his sister back. 
After their last fight, a night which he had regretted the moment she walked out the door, Charlie had been worried sick about Collins. He had no doubt in his mind that she'd slept over at John B's house, but every time he felt the urge to stomp over there and grab her, something just wouldn't let him make the move. Perhaps it was his anger, because by God, Charlie was livid. He didn't want to take the initiative to approach Collins because he was so angry, he didn't want her coming back unless she was crawling and begging for forgiveness. Why should he be the one to go out of his way when she was the one who left him? 
That mentality alone is what allowed Charlie to still be able to go to work like any other day and go on as if Collins had never existed before. And it'd worked for a while, until night fell and he was home. Every walk to the bathroom he was reminded of her when he saw all the duplicates of hers to his. The hairbrush, the bath towel, the deodorant; the evidence was all still there. Every time he got up to blow the candle out before bed, he had to stop himself from subconsciously going to Collins's room to say goodnight to her, because that's what they always did and it had become habit. 
Truth is, he missed her. 
He missed her so much it made his blood boil, because this was all her fault for not listening to him, for not following through with her side of the deal when he said he'd be more lenient with her. She was supposed to be safe, to not make stupid decisions that would get her in the exact position that she was in now. When she left, anger took her place, but now the anger was gone, and Charlie still didn't have his sister. That's why he wanted her back so badly.
The whole manhunt on John B had escalated to new heights within a day of the police's statement to the public. It had become full blown investigation into tracking down this sixteen year old kid, leading to the SBI touching down and staking claim to a section off the beach solely designated for setting up shop to track John B's whereabouts. There could only be so many places to hide on a damn island, so what was with all the commotion? 
Charlie watched as men in SWAT suits and men with button ups and ties on the collars walked around like ants on a hill, busy at work. He had his bike parked on the side of the road, close enough to the action while still trying to figure out what to do. Collins could've been anywhere. If they couldn't find Kie's car with everyone on the island searching for it and John B, hungry for the $25k reward, then what could he do? Right now, his best shot at staying up to date on the case was running surveillance of his own and keeping a watchful eye on the source of all the action. It was the best he could do with such limited options. 
He was so busy mindlessly flicking his lighter on and off in his hand that Charlie hadn't initially noticed Sarah Cameron walking up to the tent of state officials like she wasn't walking into the line of fire. Charlie immediately straightened up at first sight of her, his eyes tracking her all the way until she disappeared into the tent, his curiosity burning with the desire to know what on earth she could be doing in there. 
Daringly, Charlie started to approach the tent, despite the fact that there were officers surrounding every inch of the place. He had to know what Sarah was doing there. She and John B were involved, so did she know where he was? If she did then maybe he could follow that lead back to Collins because they had to be together, right? Wherever John B was, the rest of the Pogues followed.
But why would Sarah rat him out if they were supposedly in love? Charlie's mind automatically went to the idea that it was for the money. Of course, what's a Cameron if not awash with greed? She was going to throw their little romance right down the trash chute and collect her reward while John B choked on rotten banana peels and empty aluminum cans.