My guess is that they escaped but were blamed for killing the king of alabasta by WG. Sabo has the VC of Luffy and Vivi will want to come to SHP in case of her looking to run away from WG. Also, Sabo having the VC of Luffy is just the reverse of Luffy having Ace's VC. This has to come into play at some point. Luffy had go go save Ace, Sabo will come to help Luffy. Also, RA had clear instruction from Dragon to keep Robin safe during timeskip.