How to recover photos that were deleted during an import from an iPhone to Photos?
When images are "deleted" in Photos, they are actually moved to a special album called "Recently Deleted", where they wait for 30 days before they are actually removed from your computer. Assuming you didn't manually clean out this folder after deleting them, you should be able to recover them by navigating to Recently Deleted, selecting the photos, and clicking Recover in the top-right corner.

Here is about where Recently Deleted should appear in the sidebar (it may appear differently depending on what other albums you have):