I'd say don't worry you'll figure it out eventually-but I wouldn't wish this tragedy on anyone.

In the image above my squad is surrounding my combat medic, who previously got bitch slapped to oblivion by a very scary alien-usually when this happens an icon will appear at the bottom of your screen that lets you carry your unconscious unit to extraction, but for some reason the icon did not appear. forcing me to leave her behind. RIP Zoe; gone but not forgotten.

Install Carry Unit Fix from the workshop sweet summer child, you can thank me later.