From what I get you're at the spot where you fight Aster and Eclipse beneath the Grand Stairway with Victoria. And if I'm not wrong, you can only get out of there with an escape rope or some move like teleport to bring you back to the Poke Center
EDIT: But if you are at the spot where the Meteor people were like going all 'We Got Victoria And We Are Going To Use Her As Bait To Lure You Into The Lower Parts' place, just head up the ladder