This conversation has been merged. Please reference the main conversation: Lightroom: Smart previews disappear for modified pictures
1. Create a Smart Preview for a photo (Libraries module, Library=>Previews=>Build Smart Previews)
2. Hide the original file from Lightroom (e.g., rename the original file, disconnect the drive it's on, etc) so you're working with the Smart Preview when doing your editing.
3. Make a virtual copy of the photo (Photo=>Create Virtual Copy)
4. Delete the virtual copy
5. The MASTER photo which was not deleted no longer has a smart preview.
Smart previews should only be removed when all copies of a photo that could potentially use that smart preview are removed. This bug has persisted across several version upgrades.
I keep my primary files on a big slow RAID and edit smart previews on my laptop a lot, and often use virtual copies to have one color and one black and white version of an image. Sometimes I decide I don't want the B&W, or just decide I want to go back and create the B&W after making a few more edits to the original, so I run up against this bug a lot in my workflow.