To replicate:
- Have an initial image opened, let's call it Image 1
- Load another 3 images in Photoshop that are planned to be loaded into stack. Let's call these Image 2, Image 3, and Image 4
- Files > Scripts > Load Files into Stack > Add Open Files > Select the Image 2, 3, and 4 targeted for stack. Leave Image 1 unselected.
- Once Photoshop completes the stack > Right click on the new stack image tab and choose Close Others
- You should now be confirming each opened image to be closed. You'll confirm closing Image 4, Image 3, and Image 2.
Once you confirm the last image selected for the stack (Image 2), Image 1 dissapears from Photoshop as well. No closing confirmation, nothing. It simply disappears.