Restore the most recent backup of your catalog file before the accidental deletion. Just place it in the folder where the existing catalog is (you might want to first move the existing catalog to somewhere else just in case you need that one too)
If you know what the images are you might as well just go ahead and delete them from the disk rather than messing around with the catalogue, although you need to be sure, and if the images are in some random order, this isn't the best choice.
Or you could just re-import them (the images already in your catalogue will be greyed out, the ones you removed can be selected) and delete them again. LR will show you the most recent import, so you can pick this and see them isolated from your other images.
The latter is the easiest and doesn't involve messing around with catalogues, and you will retain any edits you've done since the deletion vs when you backed up the catalogue last.
If you do this again in the future and you know you made a mistake as soon as you did it, you can just Cmd+Z / Undo to correct the problem and start again.
Thank you for your help! I have resolved this issue and learned a few things along the way.
Thank you for helping me to resolve this issue successfully!