So, here's what happened:
1) Week before I left, the fan was rattling really bad
2) Day before I left, I replaced the fan
3) Day I left, I get several texts saying server's down
4) Day after I left, my friend staying with me troubleshoots. He reseats the ram, checks all connections, etc -- it won't POST
5) Got home today, booted, and it worked fine
I think that's really proof that, when I leave town, the server gets lonely. Nothing else could explain it!
What I really thought happened was it overheated and fried CPU. It could still be overheating -- I may not have installed the new fan right.
Anyway, I am worried about the stability. It may not stay up (that's what SHE said). I'm planning on replacing/upgrading the hardware soon. For what it's worth, I'm also upgrading my Internet connection (it'll be 10mbit upstream when I do) -- no ETA on that, yet.