As the error message says, the surface was not drawn. Because it was not drawn, it can't be deleted with Sketchup or OpenStudio Inspector tools.

A visual, simple, nothing fancy technique here is to use the OpenStudio Inspector to re-assign the Space to which that surfaces belongs. i.e.

1. create new space
2. rename new space 'delete me' via the OpenStudio Inspector
3. identify erroneous surface, and via the Inspector, change that surface's Space to 'delete me'
4. save your .osm
5. reload .osm
6. you should see the problem surface rendered in space 'delete me'
7. now that you can see it, you can delete it

alternatively, try this in the ruby console.

model = Sketchup.active_model.model_interface.openstudio_model
erroneous_surface = model.getSurfaceByName("Surface 171")
erroneous_surface.remove()