I imported images into an existing catalog and some were duplicates. It's easy to tell, because they have a little "2" in the upper left corner and are edited differently. They are the same file name, one has "copy" after the file name. When I go to delete one file, it deletes both files. I'm in "All Photographs" in the catalog. I select just the image I want gone, I tried hitting "delete"- both are gone. I tried "remove photo" both get deleted. What am I doing wrong?
These are most likely Virtual Copies, confirmed by the filename being identical. A Virtual instance shows a Copy name (and there can be more than one such), which the standard ("Master") image instance for that particular file does not. These are sharing the use of a single image file that has been imported, while each imposing (potentially) different adjustment and organisation metadata. The "2" is showing because LrC is stacking each newly made Virtual Copy and its respective Master Copy, together as a pair. When this stack of 2 is uncollapsed (just click on the 2), both instances will be seen.
You can delete just a given virtual copy, or just a given master copy, by choosing the deletion option to only Remove from the Catalog. This leaves unaffected any other instances also referring to this same source image file.
But if (when you delete a Master instance) you choose the option to also Delete from Disk - and ignore that another image instance is depending on this too - both instances are accordingly affected. Necessarily: the single common foundation which they both stand on is being washed away.