HD failure - recovery possible if system can't see drive? I've got a 2.5" SATA HD in an enclosure, plugged into a Mac Pro (trying to see if I can use Data Rescue II to recover anything). Unfortunately, my system is not seeing the disk, either in Disk Utility, nor "diskutil list." Does this automatically mean there's no way I'll be able to recover the files, and we should try a company that specializes in data recovery?
Before trying a data recovery company, you can try:


putting the disk in another enclosure, in case the problem is in the SATA/USB bridge
starting the Mac on another OS, such as a Linux Live DVD, which comes with other disk utilities, including HFS+ read/write.