Well, a little update is in order. Just the day before I was going to leave on my trip, my mandarin (who's been in the tank at least 5 months) tried to commit suicide by jumping out of the tank. I was lucky my wife called my attention to it and I immediately ran and threw it back in. It then got all slimy, with a huge amount of mucus coming off him. He was letting the current blow him around, not deliberately moving at all. I thought he was a goner. The good news on that is, he evidently has some life left in him, because he's still alive, 2 weeks later. He seems to have lost color in a fews spots, almost looking like it might look if it had gotten scraped or something. Since he appears to be acting normally now, I'm hoping his color will come back as the water stabilizes and gets back to normal.
Now, the real update; I got home, after being out for about a week and a half, and found the tank in a sorry state of affairs. Although the timers for both the food and lights had worked properly, evaporation had done a good job of trying to kill my tank. I walked in the door, and fully a 1/3 of the water was gone!!! Water was spraying like crazy from the return hoze going into the tank, since it was no longer submerged. Everything around the tank(lights, a little of the wall, some of the floor) was coated with salt. The powerhead which runs my skimmer (a seaclone 100) was totally above water! Ahhhhh! Fortunately, only one thing seems to have died from this abuse. My galaxia coral, which had one tip of it exposed to the air, seems to have bought the farm. A piece of live rock that was also partially exposed to air seems to have survived, only because the water was spraying more or less directly onto the top of the exposed part. Also, somehow my skimmer seems to be operating normally, despite the powerhead running for who knows how long without water... I think I dodged a bullet on this one; I think things could've been much worse. I shudder to think what might've happened if I'd stayed away 3 days longer, like I'd originally planned.