Well what can you do.
I have a couple of theories perhaps on how it happened.
1) I may have turned off the drive when without disconnecting safely however, I discounted this as I don't remember writing to it .. but it's a possibility and I do remember looking at the drive not too long ago.
2) Whilst using photorec on a second run the external drive suddenly disconnected and reconnected. This was on the 19th and is recorded on in the SMART data :
1,Raw Read Error Rate,51,200,200,OK,3,0,Enabled
199,Ultra ATA CRC Error Count,0,200,200,OK (Always passing),1,0,Enabled
I ended up with the above - and HD sentinal shows this happening on the 19th June - so I know it was due to that.
This kind of stoppage is pretty rare but I may suspect a usb 3.0 card Asus U3S6 which I have installed as being the culprit. I've had disconnects before on occasion but very very rare. (My motherboard is old enough not to have USB 3 so this is why that card was added). The SATA part of the card has caused no end of trouble that I had do stop using it.
So it's possible that at some point maybe this might be responsible but again logically I don't see it as I didn't write to the drive. Haven't for some time.
It's concerning though because I've never had this happen ever to me.
When I've reformatted I will test the drive thoroughly with the Western Digital Diagnostic tool to see if it detects anything. I appears healthy according to HD Sentinal
Sector 63 - yes this all makes sense as the WD Drive is a blue version which I installed at least 5 years back and when I had XP
Lady Luck: Oh yes I think that is her although she's feigning sadness for the camera.
And again thank you for your efforts and all who have tried to help. I appreciate it so much.