I have an external 1TB HD that was previously formatted with NTFS and then given to a Mac user who, probably, formatted it with HFS+, filled it with data, and then ... BOOM. Nobody can tell what happened.
My best guess is a partition table corruption, anyway, here is what I've tried:
EASEUS Data recovery, partition recovery, who did a good work in finding delete data (there was everything visibile after the process). The only problem with this solution is that it would have took 30 thousands hours to complete. I have no idea why.
TestDisk, who analyse function took 6hours to complete just a 04% and then I had to stop it.
Active@ Partition recovery, whose result is here: