It's not a subversion I think, since the trope is being used straight; it's just being used from the other angle. Transposed Trope? Reflected Trope?
Fanfic Recs orwellianretcon'd: cutlocked for committee or for Google?I think I'd call it a rather neat subversion; Foreshadowing is giving the audience some piece of information that allows them to guess some other piece of information that hasn't yet been revealed.
In this case, you've got A) the first piece of information, the one that's given to the readers: the statement that Alice, Bob, and Carol never see Dave again after they leave him behind. B) You've got the expected outcome; the piece of information the readers can guess: Dave is going to die. The subversion lies in that while it is foreshadowing death, it's not Dave's. The expectation that the statement set up is subverted.
It's a Prophecy Twist is what it is.
But yes, I would count Prophecy Twist as a subversion of foreshadowing: The wording of the prophecy leads the (non-paranoid) viewers to expect one thing, but the prophecy is instead fulfilled in a different way, subverting audience expectations.
It's only a prophecy if they are told beforehand "If you four attempt this task, one of you will never see the others again." If it's simply mentioned in the narration as it's happening — something like "Dave was sleeping when the others left the makeshift shelter. It was the last time they saw him." — that's not a prophecy.

The trope in question being Foreshadowing.
The Messiah tells Alice, Bob, Carl, and Dave that they must Walk into Mordor, to take out the Big Bad, but that one of them won't make it. En route, Dave breaks his leg, and the others need to leave him behind. The narration says they never see him again.
When the other three get to Mordor, it turns out that the reason they never see Dave again isn't that he dies, but that they do. Is this a subversion of foreshadowing, or what?