Right, I'm now at my computer and can explain properly... I'm still not sure what happened and why it did - which is a tad disconcerting but why I've now switched to daily backups for my LR cat!
I was working my way through a few hundred photos (long lens shots of my eldest playing rugby, so I expected a lot of missed focuses, wrong expressions etc. and was basically hedging my bets by taking a blast of three each time). I had done the cull down to 55 images and had processed them lightly to get WB and exposure settings "right" - which took longer than normal because of the mix of horrible incandescent lighting and daylight from windows that the hall had. I think it took me about 2 hours which is a crazy amount of time for that number of images, given I wasn't doing heavy editing at all. Colour temperatures ranged from 2250 to about 3300 which gives some indication as to the horrible conditions and because of their kit, I didn't have any mid greys (or anything without colour) that I could use for a reference point... but that's digressing from the main "problem" I had which was technological!
I was just about to upload to my website using the WP/LR plugin, so I dragged the 55 images across to that Publish To folder, which was a new collection I'd just created within my main WP/LR plug-in, which was otherwise set up with authorisation, settings etc. It was this drag and drop operation that seemed to break things. LR simply didn't do anything... it was as if I hadn't dragged & dropped anything. Now I've been having some slight temperamental issues with LR since the last automatic update (which also gave me PS 2015.5) where dragging multiple images doesn't always "catch" - I have to click and hover over the image until the stack of files icon appears, then move the mouse to where I want to drop them - if I do it too quickly, it just ignores me. Not sure if anyone else has found this problem since the last update?
Anyway, so I go to do it again but this time it doesn't even let me select and drag the files... so I decide something's a bit off and close down LR. It won't re-open, so I reboot my whole PC. That's when I find I've lost all my Publish To "things" - every one (FB - which I don't use but was set up; Flickr x2; publish to hard drive and WP/LR) is just showing "Set up" and none has the various collections/folders I have set up within each. One LR one had about 20 sub collections.
Next issue was when I go to my photos I've just finished sorting, they appear in the folder structure and are listed inside that collection I'd created within the WP/LR plugin (using the Go To Collection menu when you click on an image in Grid) - but when I chose to go to that collection, it didn't take me anywhere. Maybe not a surprise because the collection - and all Publish To collections - had vanished!
I did a bit of GoogleFu and realised I needed to create a new, blank library and import all of my images into that. That took about 3 hours. After which point I discovered those 55 images and quite a few other recent ones had lost all edits made (although on reflection nothing like the 800 images I suggested - I think I had panicked and assumed all of the last weeks' had gone but most are ok). They were back to SOOC state. So I went through and re-edited them all, another 1.5-2 hours probably (at least I didn't need to go through the few hundred I'd shot and re-cull!)
Something still wasn't right because at some point (I think Windows annoyingly did an auto-update and rebooted my PC when I left it for half an hour!) I came back to find LR was closed and... guess what... all my edits had been removed again
So I did them all for a third time. At least I was quicker this time, so it probably only took about 45 minutes. I've also stopped using the WP/LR plug in just in case that's a cause of problems. I simply publish to hard disk and then use the WP uploader in the admin console of my website.
But talk about frustrating - and odd. I'm not sure what's happening, but I now have a brand new LR catalogue which for the moment seems stable. No more losing of edits etc.
Any ideas?