I would have honestly said in the ad that it would have been a no where near perfect junkyard part.
This is one of those, crappy situations for the buyer really.
Should have given more pictures and info from the get go.
If it's not a self service junkyard, then I would have texted a picture of both sides of the mirror, or at least said it looked beat up from the inside and see if the buyer (Boo) still wanted it.
If this was me, I'd refund the guy minus the shipping you ate out of pocket, really. That mirror looks like total ass.