User blog comment:Kaido King of the Beasts/Chapter 801: Another Game of Thrones/@comment-1595565-20150924223259/@comment-10543621-20150925032828

Sanji has always had the history of doing all of his deeds with the biggest impact off-screen. Every arc, he has consistently disappeared for awhile only to return with something useful.

I guess this time, he's done the biggest thing so far. I'm guessing he has something the WG wants. Possibly information or who knows what. Maybe he stole something from them or he knows the location of something they want, hence the alive bit.

Also to note, it has to be something that involved him alone seeing how the other members of team Sunny received the generic bounty increase. Which means even after disappearing WITH team sunny, he probably disappeared FROM them by himself at some point...