Good news, everyone. My salamander is still alive and kicking after I came back from my 17-day family road trip. Judging from how empty the tank is, he probably figured out that the cherry shrimp in his tank are edible.
There's quite a bit of evidence the little guy hunted down his tankmates: some uprooted plants, changes in the sand substrate surface, and poop clusters with bits of shrimp exoskeleton like legs sticking out of them. That and I went from having like 15-20 shrimp before I left down to 5. Maybe even 4, seeing as how I can barely find any.
I'm not upset- rather, pleasantly surprised he can adapt and hold out this long without supervision. I'm just glad he's still here (and apparently not even the slightest bit skinnier, the fat little faggot).