er, no you didnt complete an earlier objective though... once you are in the desert you need to:
- hide between some rocks from scorpion fighters (which wont do anything but you wont progress the mission otherwise)
- treat the injured and tired Reman with plants and herbs you find in the desert
-find survirval items in the canyon (optionals for all 3 careers)
look at the map to find the spots, since its such a huge map you need to zoom in to see the white circles... the tricorder hels find stuff as well
After that you can enter the cave and get a cutscene that gets you to the next part of the map.