I was watching "the moth" episode from season 1 last night. Inside the cave, after Jack asked Charlie when his last fix was. He alos asked him if there were any other symptoms etc.. Charlie said
"Aside from the conversation I had with you in the jungle about an hour ago, no"
What if Jughead didn't work, and Jack, Kate, Hurley, Jun, Sayid, Sawyer etc..get flashed to 2004 and must somehow change things in that timeline? Perhaps Crazy-Jughead Jack did have a conversation with Charlie. And Charlie just dismissed it as a side effect from his withdrawals. That would be a cool twist.