I had a file which I had worked for longer time and saved every now and then. When I disconnected my laptop from dock and suspended the OS, Kate probably crashed because after resuming the host it wasn't running anymore. Reopening Kate opened an empty document, there was nothing to open with 'Open Recent' and the file I had worked with doesn't exist on the directory anymore. FYI, file open dialog is really slow as it seems to continuously hang with something. Gwenview behaves similarly and I see 'plasma-shell' process consuming quite a bit CPU at times. Kate has now become unusable due to extreme slowness.
Kate will not delete files and on save it normaly writes to a new file + renames afterwards. I am sorry that you lost work and that the system is now in a bad shape, but I think this is more or issue with a messed up suspend/restore and we can't fix this.