Am I missing something? - Early game SPOILERS

So I’ve started replaying DS2. First time I played it, I think I rushed through parts of the story and didn’t fully take it in. Going back through it now to give it another shot and take my time.

One thing that’s been hard for me to understand from the start is when Sam’s base is attacked and Lou goes missing, he immediately seems to assume she’s dead. But… her body’s not there. She’s just gone.

Am I missing something obvious that confirms she’s dead? Or is this just Sam jumping to conclusions for story reasons? I’d have thought, given what she means to him, he’d at least want to look for her or confirm it somehow.

Curious what others thought about that part — did I miss something?