Disappeared files from iCloud

iCloud has managed to simply lose a whole load of files. The folders are still there, but not the files. I've tried all of the suggestions, but to no avail.

Whilst speaking to Apple support, I realised that the disappeared files from several folders, all disappeared at exactly the same time (18:51 UK time on 24th April) - my computer wasn't even on at the time! Apple are escalating the enquiry, but I wonder if any else has experienced anything similar happening.

And since speaking to Apple, a few random deleted files (not the ones that disappeared)suddenly appeared on my desktop.

I've never experienced anything like this before - I've lost years of work - so I'd be grateful if anyone has any ideas or similar experiences to share.

Thank you.