I just noticed something rather unfortunate: i meant to import, but hit "Open" instead, so it, well, opened, like I told it to. Is the file I was working on still floating somewhere in metaspace, hidden behind an extra special alt-crtl-shift-ZZZ!!!11! key? If not, is there a way I can make it yell at me should I do this again? There was no "are you sure?" prompt or anything .. but it does prompt me every time I save, with "Save Over?" >.<

Sorry, I'm just now seeing this thread There are two places that you can find quit sessions. On my pc they're in C:tmp and oddly enough, the Recycle Bin.
There's no warning, but you could always do "Recover Last Session" in the File menu.

I'm pretty late into this discussion, but it may help someone (I hope).

Drag the preferences window down or just change the Window Type of one of your open windows to User Preferences, then select Auto Save. There is a button there to open a recent file and I think it will even consider temp files as recent.