One Still Missing Engineer

From @Iszi 's comments I have to post what happened. Hope you do not run into the same.

I first tackled the outpost where you land on X57. It is right behind you when you land. So found the body of Mendel. And how he died brutally.

Till then there were no stations marked on my map.

Then I took out the Fusion gun ahead of where I landed. Then repaired the transmission tower. Then went and got C Hymes at Survey Station 1. Recognized her death as a result of an explosion.

At this point the game did not mark her body as found. Which is why my question in the first place. I kept going back to the same station to make the game change her status to found.

Last I found the last survey station where Montoya should have been. Found all the clues to his vehicle. And then concluded that I found Montoya. But at that point there is a marker on your map about Montoya's dead body. Unless you pick it up even C. Hymes's body does not register as picked.

This is the crucial point that the Wikia article missed.

I went through with the mission, let Balak live. And then Simon is like all Where are my engineers? I was able to answer about two them found. He said please maybe the last one might make it.

Picked Montoya's body and Mission Accomplished. :-)

In my first one I did it the other way. And I tend to rely on my journal entries a lot.

Survey Station 2 has an interaction tag on east side of the bunker that says "faint footprints lead off to the east." I decided to go by foot east in case there were more clues, but the body was just due east, down in a ditch. I could have found it with the rover. I found the other two bodies first, with survey station 1 being last. It didn't register her as found at first, until I found Montoya.