Is the paint on your bike actually damaged?
If it isn't, then they aren't going to replace your panel.
Even if the coolant got on the panel on the inside, there's a sound deadening material that the coolant most likely is going to hit directly.
Not to mention, that no one can see the inside of your panel when you are riding your bike. If the coolant was hitting the outside of the panel, then something is really wrong.
Unless the coolant was boiling hot, and was coming in contact with the panel in such a way to actually warp, you don't really have any reason to request a new panel.
Coolant isn't corrosive to plastic.
BC.