Can't free up "other" disk space after deleting time machine backups

So...I was cleaning out an external hard disk that I'd been using for time machine backups, among other things. Without thinking about it, I moved the time machine backups to the trash. Yes, I know you're not supposed to do that.

I tried to move them back - but no luck. So I decided to empty the trash and get rid of them. Which was an adventure in itself. Couldn't empty the trash (and yes, I tried control-empty and all the other tricks). Tried from the console. No luck on any other choices, so I fired up the disk utility, wiped the external disk and reformatted it. Bingo - trash emptied.

But the space taken up by the backup files on my internal drive (which were in the trash) seems now to be inaccessible. I've got 160gb in "other" storage whe I look at the disk in spotlight and a corresponding amount of disappeared space when I look at it in other utilities. Tried everything I can think of, but no utilities seem to see this massive bolus of wasted space. I had 160 extra gigs of free space before I started this exercise...so something's gone quite wrong.

Trying full backup now - but would much prefer not to have to rebuild the while thing. Plus, I'm not sure if the new time machine backups will just backup (and restore) the wasted space.

Help, please?