Rayyan's sophisticated de-duplication makes it easy to find and delete both exact duplicates and ones that you've decided to delete manually. We're working on an undo button for such accidental deletions, but in the meantime, there is a pretty simple workaround described below.
- Put these entries alone in one reference file (with a format accepted by Rayyan)
- Add them back to the review.
This .gif walks through the process in more detail.