And everything worked fine. I saved my work, and then later the day I started working on it again but this time when I deleted the plane surface the particles weren’t deleting with it… So it looked like this.
Have you made sure to reset the particle cache?
For that, jump back to the first frame (Ctrl + left arrow) and
increase/decrease the number of particles by a fraction to make sure the cache resets.
If it they are still showing up you more than likely have a cached state for the emission of the particles that is prior to the mesh being edited. Free all bakes from the cache in the Particles panel and go back to Frame 1 (or whichever frame you have the particle emission start on) to regenerate the particles and begin a new cache for the edited mesh.