The Sanubia Desert is one of the areas that you can visit while on Bikanel Island.
You can come back and revisit the Sanubia Desert areas, but you cannot return to Home after you have pass through that section of the story. Refer to the strategy guide sections below for more information:
19) Sanubia Desert
The Sanubia Desert is part of Bikanel Island where you must track down each of your team members on the way to Rikku’s hometown.
20) Home
The hometown of the Al Bhed which is under siege by unknown forces.
You can obtain the 
Mercury Crest in this area. This item is needed later on to obtain Rikku’s Celestial Weapon, the 
Godhand.
The Sanubia Desert is also involved in the following side quest:
