OK, I assume that you have the lasercopy 
background, as described, and at least one 
acetate layer with the cel, which also is as 
described.  Is the top layer the photocopy, 
replacing a book set-up?  or is the photocopy on 
the bottom, replacing a second acetate cel layer?

I ask, because I have a cel that I will make a 
replacement top book layer because the character 
has a neat little blank spot that would have fit 
under the book layer, and the image doesn't make 
sense without this top layer.  Of course if I 
sell it, I'll honestly describe this top layer as 
self-created and not production in origin.

And I've seen items for sale that specify that 
the cel contains one character, but that the 
other character is on the (laser-printed) 
background layer.  These are presumably studio-
made, though perhaps not production in nature.

If it's a self-generated replacement layer, 
you're justified in a complaint.  If it came to 
the buyer the way s/he sold it, well, then it 
might just be a matter of ignorance on his/her 
part, and the fault might go back to the way the 
studio released it for sale.