Judging by the pictures I don't think those are sperm plugs, but rather the actual hemipenal glands.
They do become exposed when your cham relieves himself and usually go back in fairly quickly.
It's good that they went back in. If they were exposed for an extended amount of time.... I would keep an eye on him for a few days to make sure they stay in where they're supposed to be. Otherwise, I would guess that he had just defacated and they had not gone back in yet.
-Brad