Apparently I managed to accidentally clobber them when adjusting the wrong settings somewhere when trying to figure out why the heck the folder associated with these had just jumped all the way up to the top o the list all of a sudden (it should've been at the very bottom and out of sight!). Gah!
In the meantime, I'm going back through trying to restore broken links (by manually re-adding the offending pics). Fortunately they're all still there, though annoyingly there's no one-click "link them all back up again" magic button :/
EDIT (2am): Phew! I've just finished going through checking for broken image links and getting everything fixed up again. Along the way, I took the chance to make a few images a bit larger too for good measure :)
If you do find any broken image links/placeholders, please let me know and I'll try and fix them. Strangely, there were still a few images which I seem to have uploaded, but don't seem to be attached to any posts with broken links (at least the ones I've checked)...