Ah yes, I can see that. The gap between the first two people and the third threw me off, I thought the third person was in a different letter.
Edit: upon further inspection, the third person in the first panel is lying on their back, but in the last panel they are on their side, so I'm backtracking my backtrack.
If the people carrying the stretcher hardly move between the first and last panels, then yeah they probably aren't visible. But then it's weird how they are rearranged anyway.
I think that's a different stretcher in the last panel. The ones we see in the first panel would be loading just off to the right towards the bottom of the last panel.