Zelda Tears of the Kingdom: How to complete the Lost in the Dunes Side Quest
One of the most striking things about The Legend of Zelda: Tears of the Kingdom is how side quests might chain into each other, and how seemingly unrelated events might come around and help you down the line. Such is the case with the Side Quest Lost in the Dunes. As part of a series of Side Quests with the Gerudo Rotana, you'll be tasked with finding 7 orbs scattered across the Gerudo Desert, and one of the orbs in question can be found in Kera Kera Bazaar following the Gerudo Desert's dungeon - minus its owner, however.
How to complete Lost in the Dunes
If you try to pick it up you'll be told that its owner, Ponthos, is missing. Enquiring further you'll find out that during the attack on Kera Kera Bazaar he fled through the Western Gate, most likely seeking shelter near a tall structure. His friends, however, are concerned that he might've fallen victim to a sinkhole. Sure enough, there's a sinkhole right next to a tall structure not far from the western entrance - and if you let yourself get caught in its current, you'll discover that Ponthos indeed fell victim to this same sinkhole.
Now you'll need to help him find an escape route. Blow through the rock walls across the cave network and you'll eventually find that this cave in question is connected to the well for Kera Kera Bazaar - once the connection has been established, Ponthos will thank you for finding a way out, and you'll be able to visit him at the Bazaar.
Naturally, you'll be thanked for saving Ponthos' life - and you'll be gifted his orb as a reward. Now, getting this orb from Kera Kera Bazaar back to the Gerudo Shelter might be a bit tricky - but with a little ingenuity and a healthy dose of Zonai devices, you should be able to manage. As for Lost in the Dunes, congrats on saving Ponthos' life!