If you did remove the photo from Lightroom by mistake, then you're best off loading the latest backup of your catalog.
If you don't have XMP files written automatically, there's no other way to get your work on the photos back.
Thanks - how do I load the latest back up? Do I need to re-import the original photo files prior to loading the backup?
Basic rule: Re-import is most of the times - or even never - a good idea
- Quit LR
- Backup your current catalog (*.lrcat)
- Open the latest zip from from the backup folder and replace the current catalog.
- Start LR
Thank you - it worked to my immense relief. I've lost a few hours work but perhaps I'll learn not to do that again.