>> I got my 500 GB HDD back after loosing 2 partitions.
Conventional hard drives with their spinning disc media read/write/store data very differently than the newer solid state drives. Also all drives, either conventional or SSD, can fail or their file systems become corrupted in many different ways so recovering data is never, ever a sure thing. Just because it worked one time is no guarantee it's a sure thing.
That said, in this instance unless KimB's phone is having other issues (has it?) I'd like to assume this isn't so much a recovery-repair issue and more of a 'what happened' kind of thing. I'm really curious about that 'Vault' file or folder. Just glancing through Google Play there are numerous security-focused apps that utilize some kind of 'vault'. Are you sure at some point you or friend didn't recently install something on your phone to secure your photos? Any new icons you haven't noticed before when you open up your 'Apps'?