Lightroom folders AND photos disappeared - NOT missing
I've searched through the forums but not found what I need. Everyone seems to have 'missing' issues or a case of things merging but from what I can tell, my images have just vanished from lr altogether.
Recently got a new pc (win 10) and restored my old catalogue from external drive (where it's always been, along with all my images). Hadn't really looked at it until now but I've just booted everything up to edit some images from last year and the folders are gone. Not "missing", actually gone. I name my folders/files by date and you can see in the screen shot that 2015 and 2016 aren't there. Everything still appears to be on the ext drive but nothing is showing up in lr. The images don't seem to be in 'all photographs' or in another folder, they're just gone.
2017 just has the one subfolder it should have as I've only shot once so far this year and just imported everything and haven't touched it since. I don't even know if the folders were already gone before then or if I've somehow done something during that last upload to delete/overwrite it all. Really starting to panic now as that's A LOT of work to lose!!!
I've checked to see if they're accidentally on another catalogue but the only other one I can find (I assume what was created at install) is totally empty. They definitely aren't 'missing' as there's nothing with a question mark and they don't appear in the 'missing photographs' section, all of which are much older photos that I haven't got round to 'finding' yet.
Please please please help!!!!

