My wife had some problem with her HSF formatted drive a few days ago. The drive couldn’t mount even though the standard utilities in “Disk Utility” (verify/repair disk) reported no problems.
I found this snippet somewhere (I can’t remember where and apologize for not linking to it).
Using Inspect on the drive with problems I could see it was called “disk1s3”:
# mkdir /tmp/disk
# mount_hfs -j /dev/disk
disk0 disk0s1 disk0s2 disk0s3 disk1 disk1s1 disk1s3
# mount_hfs -j /dev/disk1s3 /tmp/disk
# diskutil disableJournal /tmp/disk
Journaling was already disabled for volume Liselotte Book on disk1s3
# diskutil enableJournal /tmp/disk
Journaling has been enabled for volume Liselotte Book on disk1s3
2# diskutil unmount /tmp/disk
Volume Liselotte Book on disk1s3 unmounted
Once that was done I could mount the drive. No data was lost.