I assume Swamp will step up and comment here, but in the meantime I suspect this is the explanation:
Swamp had to switch a lot of the stories from round-to-round in order to prevent two stories from the same author from competing against each other in the same primary round.
"Subgenre" submitted a story early in the month, and supposedly these stories are posted in roughly the order received. But because Swamp had to switch things around as noted, "Subgenre"'s story has not appeared yet, even though more than half of the submissions have by now appeared in primary rounds. Therefore "Subgenre" thinks his story has been skipped.
If that turns out to be the explanation, then "Subgenre" can relax; his story will show up, probably very soon. But Swamp is gonna have to verify that explanation.