Search the Woodpaw Gnoll camps of southern Feralas for evidence of the courier's belongings or the courier himself.
Our "friends" the Woodpaw might have gotten Raschal in the end, but something tells me that's not what occurred. Still, they're the best place to start looking.
I wish I had clearer insight as to what to do, but all I have right now is 'Search the Woodpaw camps - go.' I do know that gnolls will keep items they scavenge and fight over them; maybe they ran across the backpacks Quint mentioned. I hadn't risked a head-on fight in past searches, but with Quint's vision on this I say rip into them.